I don't actually have it yet, but if someone has an invite to spare, I would love you forever (firstname.lastname@example.org).
As for replacing Facebook, I doubt it, thought I'm not even on Google+ at this point, so I'm just going by what I've read. Perhaps it will blow me away, and my opinion will change, but I just can't see Facebook going anywhere. The only way people would go through the inconvenience of recreating their 'social network identity,' and restarting their quest to a kajillion friends is if Google+ offered something so unique and so much better than what Facebook offers, and I don't think they'll achieve that. (And even if they do, Facebook can just incorporate the best parts of Google+ into their own network, as they've already shown they have no qualms with changing things up.)
If it were still targeted solely to a single market, like it was in the beginning (i.e., college students), I'd say it was possible. Now, however, we've got everyone and their dog on there (literally - I'm pretty sure there are Facebook pages for dogs). And for older generations - my parents, for example - there's no way they're going to make the switch, and in turn, they'll keep me from going doing so either. I wouldn't mind starting up a Google+ account, but it certainly wouldn't replace my Facebook one.