Keep off Vista though - despite what TB says, Vista was rushed out as a "replacement" for XP, and was poorly implemented by MS - it's very resource hungry, you will need a pretty hi-spec PC to get any speed out of it.
Its not so bad. Its biggest issue was being 'different' and needing new drivers. This caused the idiot IT journos to say 'it is crap' (these are the idiots who believe running as a non-Admin is a slur on their manhood, and exactly who UAC was aimed at) and hardware manufacturers to blame it for their laziness and sloppyness.
Yes, boot up time was a bit long winded on crappy hardware (I always said it needed at least a Core2 with 2Gb to run properly - way more than XP, and about the same as Win7), but give it good hardware, it was fine. My Dell desktop, which I still use, when I first got it, would go from power on to full, usable Windows desktop in 11s with the crappy Dell build

The XP v Vista debate was no different to the Windows 2000 Pro v XP debate, when everybody hated XP because it was different to Windows 2000 Pro, and there were many driver incompatibilities.