Vista is not at all a "bad OS." The upgrade path from XP to Vista may involve a hardware refresh but the OS itself is solid, attractive, and pretty user friendly. I've been running it for about a year and it has yet to full-on crash on me. In fact its ability to isolate faulting apps is excellent.
My Fedora10 system, by contrast, has way more quirks. Yes, it's apples to oranges when comparing the two for all the reasons we know about.
While I don't usually stand up for Msft, this "it's a bad OS" conclusion is not fair. Which isn't to say Msft didn't fumble in so far as not doing enough to get drivers rewritten or having awful, awful marketing (The Seinfeld ad was enough to turn anyone off the OS).
What really sucks is that XP is a just-fine OS as well.. but if you try to config a system on Dell now with XP it is an EXTRA $150 (!!).