From my research my impression is that Google+ is the 'adult' version of Facebook. The ability to have 'circles' and keep followers in separate groups is what makes it special. I don't want everyone seeing everything I post.
One could argue that Google is taking over the world but their product is great. Gmail and Google docs as well as Picassa, provide me with all the cloud memory I need. These options have been available for what seems like years. It surprises me that Apple followers think that icloud is something new! At present google+ hasn't nearly the following of Facebook but I think it has a good chance of becoming more popular.