Update: The thing is frickin' bomb.
After working on it (installing Office, iWork, you name it) for about an hour then grabbing my 17" 'book I was amazed at the difference. My notebook feels like a big fat dinosaur.
Of course the 'Air does not have a DVD drive (you can USB one though, that's how I installed stuff), it does not have an Ethernet adapter, and Apple only sells a 10/100 USB adapter, so if you require gigabit your SOL. But the battery life is hot (rated @ 6 hours, we've seen about 5 and still doesn't need to charge) and the display is gorgeous. Keyboard feels just like mine. The think is so damn thin that it almost feels like you could use the edge closest to you to slice bread. Boot time is just several seconds - the SSD in the thing makes disk access amazingly fast. Shut down is in about 3 seconds. Sleep and wakeup are as fast as you open/close it. This is going to raise the bar. The price point is very reasonable for what it is and the bang-for-buck (given what bang you're looking for are the items I've outlined) is excellent. The quality of the engineering is evident in every millimeter on the thing.
Will I get one: absolutely not. Well, not in anything resembling the near future, anyhow. I use my iPad for virtually everything I do as a road warrior except for when I need something really special (serial connection to something, read/burn a CD). When I need a lot of mobile horsepower I drag my incredibly heavy, clunky and undesirable notebook 17" MBP

. I have less and less tolerance for having to carry anything so obtrusive. Interestingly, I don't even like reading my daily RSS feeds on OS-X anymore - the pad readers are much nicer. Feels more like I have a book/mag/newspaper in my hand.
But for PinkHat: She needs more than a 'pad when she is consulting, but equally dislikes carrying her notebook. This little device is 100% perfect. Since I am now starting to move all of our document storage out to the cloud it makes even more sense (The piece missing is to push all of my movie/music content out there - but I'm going to wait to see what Apple does first. I've a feeling they'll do a better job than me). So since she runs Windows from our cloud, runs client apps from our cloud, has a couple different access options now (VPN right into her machine, MobileMe cloud, our storage cloud) the lack of TBs of storage is immaterial.
Net-net: Apple has done another fine job of slicing right at a particular user-niche and raised the bar for it. It is NOT the do-everything-be-everything notebook. If you choose to carry/use a single machine I don't think this is your bogey. But as a mobile companion to a more sophisticated rig it is excellent. 9 out of 10: the 1 point is that I think they should still keep a wired ethernet, but I get why they excluded it.