I don't miss anything in windows7 and obviously they aren't on the same hardware, so couldn't comment.
I honestly don't feel there was ever a killer feature in win7 that I need/must have or don't already have in XP or can't get from another application. Yes there are some nice things, but would I pay over £100 to update to win7, absolutely not.
If my personal s*dd**g forum stalker would purchase a legitimate retail copy of window 7 Pro for me then I might just consider upgrading, otherwise he can sod off.