For me, so far, I don't see anything that makes it significantly NotFacebook.
Although, simply by NOT being Facebook or MySpace is a step up.
I *do* like how granular you can get with putting people into specific groups, and the Hangouts are cool for people with webcams. ;)
There is huge potential here, that's for sure. It just, right now, isn't quite standing out. For me. But that's because I don't have friends. ;)