Maybe no one, at least right now, according to this blog post from PC World’s Tom Spring. My favorite line from the comments section (which are well worth reading too):

There are plenty of users out there who don’t want Vista. And why should they? It’s bloated, buggy, unstable, requires twice the hardware specs of XP, isn’t compatible with most of their existing apps (including ones from Microsoft), and runs slower than XP (especially if you enable all the eye candy).