Ahhhh, Windows Vista... the Windows ME of the NT line....
Having quite a bit with Vista, I've found that the hardware support frankly sucks for anything more than a few years old, the software support reeks as well (No 16-bit VM support, so if you used any really old programs, you have virtually no options.
But that's not the problem most folks have with it. The interface and how everything seems to work has changed drastically from XP/2000/etc, unless you set it to classic.
Search frankly sucks.
Microsoft's Virtual PC VM software (while free) is craptastic compared to VMWare, but if you use old apps or games, it's pretty much the only game in town.
(VMWare still isn't nearly as fast as it should be, but it allows old Windows apps to be run unlike DOSBox,)
And those gahdamn security popups "You're about to run xxx.exe.. Allow / Deny?"
Sure, you can turn most of that stuff off, but I've always been a firm believer in OSes that do their job and stay the hell out of the way of their users, not constantly bombard them with useless crap warnings (which in theory should help keep your machine more secure, but in practice don't seem to work that well,)
And like ME, I expect Vista will quietly fade away while Windows 7 becomes the OS Vista really should have been.