I've had the phone for almost a month, and I've only used Google+ once and Google+ Messenger three times. I've been on Google+ since its beta, but even then I nor anyone else I know uses it. Facebook is the dominant social network with Twitter following behind. Heck. Even FourSquare and Tumblr are more prominent than Google+. Google arrived too late on the scene and while Hangouts and Circles are neat features, Facebook hurried itself to integrate its own versions of them and update the look before Google+ went public.
The Google+ features are nice, but are basically worthless. If the social network was something as big and great as Facebook, I could definitely see it being a strong marketing tool to sell the phone, but because its not, its taking up space. You can almost call it bloatware at this point.