All in all, I find Google+ quite interesting with the circles system. The trouble is that, once you sign up for Google+, your Picasa (and other Google services) don't look and behave the same anymore. Pictures sharing can then only been done with Google+ contacts (or with everyone on the internet... no way !) and for the contacts, not possible anymore to download a whole album to their Picasa, and so on. I killed the G+ thing to restore all the lost functionalities.
Plus, everyone I know is on Facebook, you have to be a geek or IT related to even know what G+ is (which is not the case of Facebook), I can't bring them all to G+ and kill my facebook account so like many people, I stick to Facebook because I don't want to spend my time maintaining my profiles in 10 different social networks... I think that may persons enrolled in G+ were just gmail or picasa users who clicked yes on an invitation but never ever gave it a look, which explains the skyroketting amount of users and the lack of time spent on it...