Heyyyooo let's not turn this into a ridiculous Apple versus Microsoft debate.
There are lots of positives and negatives to both platforms, and arguing which is better and who ripped who off at this point is really silly. While I think early on Microsoft did crib a lot of UI ideas from Apple, it's also true that Apple admittedly lifted a lot of concepts (the core of the desktop metaphor-based GUI and the popular application of the mouse) from Xerox PARC
At this point, though, I think both companies borrow from each other's operaing systems in equal parts, to keep up with each other. Vista and XP both lift pretty heavily from OS X, but OS X has some features that were built into it for the sole purpose of competing with similar features being developed internally at Microsoft.
(And for the record I've been an Apple user for 20 years now. I still am primarily a Mac user at home, and only use PCs at work... and for the occasional round of Half Life 2 or Worms Armageddon at home since I can't get those on my Mac