Look what I just pre-ordered...
I already have a 13" PowerBook that is a little over 2 years old. The battery now has a 45 minute life, it's scratched a bit, and I think it needs a rebuild. With my new job (!) I'm going to become a bit of a power commuter, and want a machine that is ultra-portable. The original reason I opted for the 13" PB was because of the portability, but the MacBook Air is just that bit more portable. I know the battery can't be replaced by mortal men, and that it only has a mono speaker, and that it has no internal optical drive, but the portability and battery life for me is the key.
Oh, and it's as sexy as hell.