I took a look at the Google+ website, just to see what it's like. Compared to Facebook, there's not much different. You have "circles" instead of friend groups, though I suspect they work a lot better, and the "spark" feed of things you'll probably like. The thing that really caught my eye was "hangout" video chats, which is an idea I quite like. The closest equivalent on Facebook is text chat, and that's a bit more attention-intrusive to my mind. You need to check who's online, see if they want to chat, and type for every sentence, which is nothing like real life.
Hangouts looks friendlier, like just turning on your webcam while you watch TV so that friends can virtually drop in and say "hi" or just sit there with a live video feed of you to keep them company. I think I've mentioned always-on video chat as the next step up from always-on internet, and this is getting to that point. Or it could be very useful for business conference calls, too, especially with the way it displays the current speaker big at the top. I approve.
The other side of this whole argument, of course, is that Facebook is well entrenched now, and it will take a giant heave to get it out of the way. Google+ might be capable of that, or it might just be a little blip. The most I am willing to hope for now is a fire lit under Facebook's collective rear ends when people ask "Why aren't you doing XYZ like Google+?" And that's a good thing. Competition is good, and Facebook has had far too little competition for far too long.
Mokalus of Borg
PS - The progression from one social network to another is part of their life cycle.
PPS - Maybe Zuckerberg missed his big chance to sell, like MySpace did.