Not really. A Sony TZ is an engineering marvel, relatively speaking. An Air is merely a marvel of marketing combined with the best that Apple can do in terms of shrinkage. They've taken the usual Apple 'smoke & mirrors' approach, this time making the machine look razer-thin by sticking with an almost-normal-laptop area. A true subnotebook with the same vertical dimensions wouldn't look as thin to the eye.
However it has a use for us business types who doesn't need the power of an MBP but likes to carry lighter stuff. To my Windows eye it's a bit crap, but it's the only choice I have for a truly portable OS X machine. I also think it's the prettiest Apple laptop out there, but that is subjective, and subject to review after I've used the Airs for a while.