For me its all about mobility. I travel by air most weeks and find myself working on planes, in hotels, and varied remote offices where space is at a premium.
I find the MBA11 plenty powerful for all my routine activities in the IT consulting field (Office programs, Databases, Drawing tools, Virtual machines, Software design and development tools etc). Its faster in everyday use and most benchmarks than my uMB or my previous RevC 2.13/2/128 MBA and runs cooler and quieter. I was worried about processor speed and screen size/density but neither have turned out to be a problem for me and the 4gb of ram is a very welcome improvement. Moving my dock to the side of the screen rather than the bottom made the 16:9 aspect ratio transition a lot easier for me.
It has a lot of things going for it for a frequent traveler
1) Enough power and capacity to use as a primary computer when traveling (and darn near enough for me when local when I add external storage).
2) Thin, light, and small area and volume that makes it easy to carry and use on small surfaces (like an airplane tray with the seat in front of you reclined).
3) You don't have to remove it from your bag for the TSA which saves more time and effort than you would think going through airports.
4) Great keyboard, good screen (although I'll use a bigger external monitor for longer work sessions when available), and good battery life.
For me this is my favorite Mac yet but I can see where the compromises made for mobility would not make it a great or even desirable machine for everyone.
