We hang on to things for far to long. I know people have a love for Xp because it just worked, friendly to just about anything thrown at it. Do is about as friendly as it gets.
But I'm waiting for the full blown 64/128bit world, to finally arrive.
Windows 7 and Windows 8.x just work too. Better in fact. They have newer built-in drivers. So if I install Windows 8 on a relatively new system, it will automatically have the networking drivers ready.
Also, the new UI enhancements in Vista+ are worth it. I keep running into XP computers that have issues with the screen not drawing properly due to the way it handles the graphics (moving the window will leave a trail if the program is not responding or something else is going on).