I guess the new MacBook Air is cute and optimized for, uh, thin. Otherwise, I think it is overpriced and under-featured. Thin is nice, but I can’t ever think of a time when I though, “I can’t use this darn laptop, it’s just too thick!”. And the non-user-replaceable battery is a joke.
Now a pen-based tablet (ok, it can have multi-touch, too) in a slightly smaller form factor, running full OS X; THAT would be cool and useful. MacBook Air? No so much.