It's as simple as this:
You use a mac running os 9 and then a mac running 10.9 , and in 5 minutes you know your way around.
You use windows XP and go to 8 and you're like : soo , how the hell do I shut down this thing?
Windows 8 is not an advancement in User Interfaces, it's an ideia that shouldn't have come out of the lab as more than a theme pack you could install if you're into touching your computer (in other places than the keyboard).
That sounded weird.