The way it keeps similar icons together in the taskbar, even when you've got them degrouped. I like it, it's just different. There's also that little desktop button at the lower right. Weird thing. The Explorer interface revamp also takes some getting used to, including the way searching is done now. I like that the new search is actually pretty powerful, but to get good results out of it you have to really know what you're doing. Gone are the rather explanatory search dialogs of XP.
I also turned off the fancy shmancy interface so it looks (sort of) like Windows 2000, just the way I likes it.

Yeah, I don't even use a background wallpaper. I am a no-frills kinda guy when it comes to my operating systems. (But then why am I using Windows? Games.)