With Windows Vista lunching approaching below are some site which give you more user experience on it.
http://www.windowsvista.com - official site
http://www.windowsultimate.com - for Vista Ultimate users
http://www.windowsvistatnt.com - Tips & Tricks
http://www.showusyourwow.com - "Wow"
BTW I just install OS X Tiger 10.4.8 and learning to use it.... from my pass experience I think I will still stick to XP for many months and changing to OS X did not make sense for me.