I originally wanted the 4GB version but wanted to purchase in the retail store more, and they only were stocking 2GB versions. So, after trying it in the store with the apps I normally use, I bought a 2GB 13". That was 1.5 wks ago.
Fast forward to two days ago and an odd hardware test result prompted me to bring it in to the Genius bar, and they decided to swap it for a new one to be safe (turned out it had the same error but that's another thread). Of course, my store is now stocking the top-end 13" with 4GB for $200 more, and for a split second I thought about requesting to pay the difference for the higher spec model.
But honestly, I'm so impressed with the machine as is I couldn't even justify spending the $200...not that I think $200 is a lot for the extra CPU and memory, but because I don't think its worth it to me. When I first got the machine I ran some tests and posted my results in the 2GB vs 4GB dilemma thread. Basically, running CS5 apps, Office 2008 apps, VMWare Fusion with Windows XP, Xcode, Mail, Safari and others all at the same time and this little 2GB Air doesn't skip a beat, nary a beachball in sight. I'll think I'll put the $200 into the Mac Mini HTPC upgrade fund for the future instead...