Vista is a perfect example of why I don't jump into any OS just because of how new it is. It took me 1-2 years to update to Windows XP (from 98), and I'll probably wait another 6 months to a year to install Windows 7. I've never even tried Vista. I have however, reverted several of my friends computers from Vista to XP. XP is very susceptible to viruses but other than that (and even then it's few and far between), I have 0 problems with it.
I've had 3 operating systems in my life: 95, 98, and XP. I also had FreeBSD installed on separate box but not as my primary OS.