Although I've just played with G+ (I'd like to call it this way) for about an hour and, while there is a lot of existing issues that Google Plus is nothing compared to Twitter and Facebook, in particular, I give it a qualified “thumbs up.”
I like it, for a few reasons: One, their "circles" feature makes it easy to organize the people you connect with; two, the interface is clean and minimal but effective; three, it’s not yet clogged up with bots and announcements from games and other apps. So in short it's clean, easy to use, not obnoxious.
Is it perfect? No, but it’s better than what I expected it to be.
There is just one thing that I would like to see on G+ and that is some kind of a personal messaging system – something like inbox on Facebook. Either that or make the “Send an email” button on Google profiles so people are able to reach each other privately and still got notified of that.
Hope this helps!