G+ is too damn confusing. That is all.
I don't put people that are not on G+ in my circles so when they sign up, they see an empty feed. Facebook knows that you need a minimum amount of friends in order to find the service useful. With G+ and the circles, this threshold is higher and more difficult to reach as there are less users.
I don't think G+ will be a "social network" like Facebook. And that's a good thing. There's a reason im not on Facebook but I still use Twitter and G+. A lot of the people I talk to feel the same way.
What's more interesting to you... A) Reading about your friend's drama issues or B) Reading about the latest, coolest startups and technologies?
A) Facebook B) G+