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...
I agree with all those saying that with the slow-to-non-existant adoption of G+ with friends/family it makes it difficult to make it an "everyday player" IMO. I ditched FB years ago when it became bloated and crap for security/privacy. IMO G+ is much better but with hardly any friends/family...what's the point?
Everyone that I know of that has tried out Google+ has stopped using after a couple of weeks. Most people have become quite established within Facebook and really don't want to start all over again with Google+.
I think Google+ does a lot of things much better than Facebook does. The problem is that you can't have small groups of people switch. Then they'd be by themselves without any of their Facebook friends. You have to get large groups of people to switch together.
I'm wondering if their numbers only include people on computers. I love G+ but I never access it from my computer. I use my phone. It's always on my phone. Does that mean I'm not part of their demographic? I'm pretty sure I'm not the only one that uses G+ this way.