OK, anyone who posted earlier in this thread about waiting for Rev. B, here's a piece of advice.
DO NOT UNDER ANY CIRCUMSTANCES GO NEAR AN APPLE STORE OR OTHER MACBOOK AIR RETAILER UNTIL REV B's ARE SHIPPING.
Why? Because I went in to my local Apple store yesterday and handled one for the first time. I was blown away at the ergonomics and aesthetics of the machine. Technolust hit me in a manner similar to when I first experienced the iPhone. The MBA is gorgeous, handles beautifully, feels absolutely solid and makes everything else feel HEAVY by comparison. It's hard to describe just how lovely it is and how PERFECT it is a replacement for the 12" PowerBook.
I would have bought one right there if they had been in stock. Really. Only when I got home did I rationalize, but I can't get the thing out of my brain. I spent last night deleting junk off my PowerBook to see if I could live with 80gb HD.
I don't think I have the will power to wait until Rev. B hits, so if you, like me are waiting for a rev. b then stay away from the stores. The MBA is hard to appreciate until you handle it. Mark my words, this thing will sell like crazy despite the shortcomings.