Driver concerns:
Though older hardware may not have drivers from the manufacturer, Windows Vista may have a generic driver for it. This is, basically, like a generic drug from the pharmacy. Its the same thing, but it costs less and it is used as a substitute. Now, yes, of course, XP does have the same support, but I cant come up with a contradiction, so this really hasn't changed much, except that newer hardware will work better in Vista than in XP, though, I doubt that hardware companies will just stop supporting XP all the sudden... SUPPORT LINUX FOR ONCE, BROAD-COM!