I bought the 11.6, and I really like it. I did not buy it for need of another computer though. With an iMac, MBP 15, MacMini, Toshiba NetBook, 2 iPads, a couple of PC Towers, Servers, Storage................
The big motivation for me was size/performance combo. I originally bought the MBP 15 to use in my office, with three monitors. I prefer a laptop with its built in UPS etc. I got so used to all of the features, I could not make myself take anything else on the road, and I am on the road alot. My wife and I use iChat, now FaceTime, every night. I use Virtual Machines on the MBP, but decided to use BootCamp and MacDrive on the MBA. It is not like it takes a long time to re-boot.
I am loving it so far, and even Windows 7 is impressive on this thing!