Both wonderful and terrible and highly dependent on your requirements.
This is a very in-depth review so if you want to get to the point I suggest skipping to the last paragraph.
I might not have much to say that hasn't already been said several times over but I wanted to give my take on this laptop as it's can be a difficult choice to make and perhaps I can be of some help. When the Air was released I thought it was the height of frivolity for Apple but I've since come to understand it better. I spent eight days getting to know it in the standard 1.8Ghz/64GB SSD configuration and I'm still wavering on whether or not I want to keep it. I'm writing this review on a MacBook Pro that has been configured to be almost the exact opposite of what you'd get with the Air. When I bought the Air I wanted to see if I could handle such immense limitations being so used to the freedom of maxed out laptops and desktops. As I'm writing this the answer is "kind of."
The MacBook Air in my opinion is ridiculously expensive. It's also ridiculously cool especially when it's closed. In fact every time I found something I didn't like and soon closed it to let it sleep I had difficulty hating the thing because it's just so cool when it collapses to be a thin sheet of metal. Every little nuance of the outer design is elegant and perfect--visually that is. There are a some hardware flaws that may or may not upset the user and one that in my opinion throws the machine's worth into question. Let's deal with that first.
As someone who thought he used several USB devices I found that I really do not. I might use two at a time namely when importing footage from a video camera into the computer and saving it to an external hard drive. An important thing to note is that while the Air is certainly not made for video editing it manages nonetheless. It can be done and it's not as horrible as one would imagine. Having one USB port also works just fine in pretty much every other case. I did get a tiny hub to use with the Air but as it's tiny it's not a nuisance to carry and generally doesn't get carried around anyhow. If I'm editing I'll usually edit at a home (not mine as I'd use a desktop machine at home). Although it can get by I would never recommend the air as a video editing machine. This probably goes without saying. Still it's good to know that it can if it has to (even with Final Cut Studio's lack of support for it's integrated graphics processor).
Many people conclude that the Air is impractical as the machine does not have an optical drive. If you live by CDs and/or DVDs then yes it probably isn't practical for you. I never use my optical drive in my MacBook Pro. If I want to watch a movie I rip it first. Most people do the same with their music so I don't think it's fair to cite this as a reason you'd need an optical drive. This does assume of course that you have another machine with an optical drive. If you don't and you want the Air as a primary machine then you will absolutely need to purchase the optional Super Drive Apple offers. You might think of going with a cheaper drive such as the ones Lacie makes (which are good) but I wouldn't as even the Air with it's added USB power cannot power them. The one Apple offers doesn't cost much more and is worth it if you have no other machine. But if you do and you don't want to travel around with a drive (like me) there's another nice solution that I found worked very well. I bought a few 8GB flash drives which are comparable to the speed of a DVD (if not faster) and hardly cost anything these days. I loaded the MacBook Air's installation media on one drive and made it bootable so I could restore the operating system or boot from the media while traveling should the need arise. I used one drive to hold a few movies I wanted to watch and another for any vital software I would need to install should I need to ever wipe the Air's drive while traveling. I bought four 8GB drives but only used three to do all of this. For less than the size of three fingers you can easily prepare for the worst and bring along some entertainment. If you want to bring along several more movies and music an iPod is a good choice. You can always hook it up to the Air and play the movies/music through the machine.
I wanted to save it for last but it makes sense to address the biggest flaw of the machine now. As I've said this is not a video machine. It can be a video machine under very specific circumstances but it is not apparently designed for use with any video at all whatsoever. I say this because of how the Air handles heat. The graphics processor (GPU) warms up rather quickly even if you're just browsing the web. Watching video on the Internet or even on your hard drive (perhaps something you downloaded from iTunes generates quite a bit of heat. When the machine grows too hot the first thing it does is underclock the GPU. Imagine watching a movie at about 1 or 2 frames per second. This is what you can expect when the Air gets too hot. If this wasn't the case I wouldn't be so conflicted over the machine. I can let go of doing any heavy media work with it but I can't let go of being able to watch a TV show without it skipping. You can work around this terrible design flaw by giving the air vent plenty of room to breathe. What I did is put the sleeve I purchased under the Air and then rested most of the air on it. I let the back section with the air vent hang off the edge so it had space to vent. This worked perfectly when the Air wasn't hooked up to external power. When it was it became a problem. It was an issue on an airplane though and the short power available on the flight may have been feeding more power into the Air than it should have. The Air exhibited some strange behavior when plugged into the power port on the airplane rendering the trackpad pretty much useless. The Air seemed to hold up just fine when it had breathing room when plugged into a normal outlet. Nonetheless this trick is annoying and is even required when the Air is on a desk or table (though you'd get through a sitcom without any trouble if it's on a desk). The computer should be able to play back an MPEG4 or H.264 file without skipping throughout the duration without special treatment. If you have no interest in doing anything with video watching or otherwise this won't be a problem for you. I just can't imagine anyone using their laptop these days without watching some sort of video online or on their machine. I see this as an enormous drawback and will be the main reason I return the machine if I decide to do so (and it is what I'm leaning towards).
But moving on...
Perhaps disk space is a drawback? I thought it would be for me but I found that I only used about 25GB once I loaded on everything I felt I needed including my entire music collection (which is only about 9GB and not the norm I'll admit) and photo library. I also loaded about 3GB of e-mail Final Cut Pro Final Draft Adobe CS3 (without Illustrator and InDesign) Episode VisualHub and several other pieces of software. I installed almost every piece of software I have on my MacBook Pro and left off the things I've either never used or used so rarely I forgot I had them. I didn't miss a single thing. I certainly use the majority of my MacBook Pro's 250GB disk and have so much data on external drives at home that it would scare you (I never throw anything away) but in terms of what you actually use I'd bet you'll find you can fit it on a 64GB or 80GB drive very easily. You did a few years ago right? Perhaps you're still doing it. Either way there's an easy solution. Buy an external hard drive. Some might argue that this is sort of counter-intuitive as the point of the air is to be pretty much non-existent. Adding things goes against that mantra. Well yes but again you can leave this drive at home or where you're staying. When you're walking around with the Air you don't need it. When you go back to your hotel your friend's house or wherever you're staying you can pull it out of your other bag (the one you used for clothing etc.). If you're at home well then you certainly have somewhere to put it. Rarely will you have to take it with you and it's not like it's that big if you do. I have a couple of Western Digital 250GB Passport drives (in black if you're wondering) and they're great. I don't see drive space as a drawback at all. It's a problem easily solved.
There may be questions for some if the SSD is faster than a standard hard drive. For random tasks yes very much. OS X is good with caching common tasks such as launching applications you use often so while application performance is definitely faster via SSD the crappy little 1.8" iPod hard drive the standard model has will not slow you down too much once the Air gets to know your habits. Startup isn't as instant as everyone says but you can immediately use the machine after startup. I'd much rather have an SSD over a hard drive as the speed increase is very noticeable but my main draw to the SSD version of the Air was for data security. It's just less likely to die and that is very appealing to me.
Speaking of death battery life is what you'd expect from an Apple Laptop. In fact I might call it both better and worse. During my tests I went to a coffee shop to write for a few hours. I left with about 30 minutes left on the battery having used it for two and a half hours (give or take ten minutes). I wasn't playing music browsing the web or anything at all. I had the wireless off. The only issue is that I was in direct sunlight and countered it with the display at full brightness (which is completely and wonderfully visible). For a battery rated for five hours under wireless use with the screen not much dimmer than full brightness I was a little disappointed that it only made it what I assume would have been three hours without wireless. Nonetheless I rarely use my laptop without plugging it in so it's good enough for me. Still I fully intend to use the battery more once they figure out how to make it last a full day. Imagine that...
The power cord is so small you can easily take it with you. Actually it's really not that small if you think back a few years when we used to have G4s. It's terribly small compared to the existing adapters and the way the mag safe attaches is so much nicer than it is on any of Apple's other laptops. It doesn't fall out by accident still comes off easily and doesn't get pushed out of the way by your knee/leg when the machine is on your lap. I hope this is how all Apple laptops are powered in the future.
I have nothing to say about the micro DVI port because I haven't used it. I suppose I could but I assume it works fine. There's not much to screw up. One thing to note about the ports though is that despite the beautiful little hatch they're housed in they are a bit difficult to use. It requires slightly more concentration than the average port when plugging something in. It's not a big deal but it might be a bother at times.
The built-in speaker is awful but everyone knows that by now. It's a single channel speaker. If you're the type who watches movies with friends on a 13" laptop this might be a problem. I don't know any people like that who don't do so at home and plug in a pair of speakers they have lying around. If you're by yourself you have headphones. I wish the speakers were better but I don't see this as a drawback.
The keyboard is a pleasure to type on and the backlight is far more effective on the Air than it is on the Pro. The keyboard also seems to be better-crafted than both the standard MacBook and the the wired/wireless keyboards (I'm typing on a wireless now). I don't know how that could be but it is. Maybe it's just because it's new and I'm now used to typing on the "chiclet" keys.
While a little heavier than you'd expect the Air is fairly light. I think the main thing to look at when considering weight is if you can safely hold it when gripping with one hand (without fear for your wrist or the laptop's safety or both). The Air has no problem in a single-handed tweezer grip and your wrist will be fine as well. It is as minimal as they say it is and will pretty much fit into any bag you've got. I thought I was going to need a new bag but found that it fit into an old one I usually carried when deciding NOT to bring a computer. That was a very pleasant surprise.
Still despite the fun of it and all the nice little benefits it has I cannot get over the situation with the heat and the GPU. It really ruins the machine for me. I think that regardless of whether or not this will be a second computer you can make the determination of whether or not to buy fairly easily. If you were once a boy scout (meaning you always like to be prepared) and/or you've recently told yourself that you need to clean get rid of stuff or simplify your life you will have trouble with this machine. There will be things you won't like perhaps to the end that you won't keep the machine. But if your life in terms of technology and other things (literal) is already simple and you don't dwell on preparedness too often you'll probably enjoy this machine very much. If all I did was write or all I did was write code or all I did was write school papers and surf the web this would be an overpriced but very capable machine. I kind of saw it as the writer's dream machine which is why I got it (I'm moving into that field primarily now) but I have too many interests for the Air to handle. I might just keep it because I'm currently overpaid and I wouldn't mind it as a backup/travel machine but I'm mostly feeling it was the wrong purchase and I'd be better suited by a cheaper standard MacBook for a backup laptop (especially since I can mirror the data and I love the black MacBook). While I absolutely hated it when it came out I've since found that it really is a machine well-suited for certain kinds of people. If you've got the money and intend to be gentle it's probably a good choice for you. If your laptop is a third arm I'd suggest holding your breath for a year or two.
UPDATE:
I have good news. I decided to keep it and turns out that I had a bad machine ("had" being the good news). I took it in because the trackpad clicker button didn't work very well and they gave me a brand new machine (very very nice of them). Not only did that resolve the problem I took it in for but I no longer get horrible choppy graphics when using the computer on my lap/in bed/when the vents are partially blocked. While I've heard gaming won't survive under those conditions this is a MAJOR improvement for me. If I could I would change my rating to four stars. The Air pretty much does everything I'd want it to at this point and the solid-state disk makes the majority of things I do much faster than the standard 5400RPM hard drive I have in my MacBook Pro. I judged the machine too harshly in the review because I thought I had a model that worked properly :). I am very pleased with it now that it can do what it should be able to do. I'm looking forward to finding out if it can even handle some light video editing.
Also I got a Transcend 32GB flash drive as a supplement. So far I haven't used it for anything than taking a bunch of movies and TV shows along with me but it's a nice alternative to a traditional hard drive if you don't want the bulk but are concerned about the spacial limitations of an SSD.
More detail ...
