To be fair, Vista SP1 isn't nearly as bad as people make it out to be (that's what I have on my office PC). It isn't as nice as OS X or even Windows 7, but the issues people had with it in the beginning were mostly because Microsoft foolishly let PC manufacturers slap "Vista Capable" stickers on all kinds of PCs that had no business running anything as resource intensive as Vista. It would be like Apple slapping "Lion Capable" on a Core Solo-equipped MacBook ca 2006 and releasing it today.
A new MacBook Air is capable enough to run Vista without any major problems, and Apple ought to have accommodated Vista since the drivers for Windows 7 and Vista aren't all that different. Some Mac users need Windows occasionally, which is why Apple issues Boot Camp in the first place.