I received an invitation and of course joined up. I have to say, after getting it somewhat organized and posting a few things, I really like this new social media. I especially love the circles, with them you can target who sees your posts, which can be useful. For example, say you're a big gamer. You can name one circle after the game you play and put all your gaming buddies in that circle. When you post something about the game, you send it only to that circle only if you want...you do have the option of sending it anywhere you want or just make it public, too. By the way, for me it's much faster than Facebook.
If you get an invite I would recommend you try it out. If you already have a Google+ account, add me!