Dell made a laptop with similar specs called the 'Adamo' for a while. It's small, light and sexy, costs about half as much as an MBA, and Ubuntu worked out of the box.
A good alternative if you'd like to avoid the Apple flavored kool-aid.
Lenovo's about to release the ThinkPad X1, with relatively beefy specs and the MBA's form factor. Do want. It's freakishly expensive though (almost $3K).
I couldn't find the "Adamo" listed on Dell's US website, but it is listed on Amazon[1] for ~$1261. That's only a touch less than a MacBook Air. Where did you find it for "half as much?"
A good alternative if you'd like to avoid the Apple flavored kool-aid.