I, for one, don't really use Google+, but it's not because of any particular problem other than, "No one else is using it," with just a smidge of "I don't know what I'm supposed to be using it for," thrown in.
It does seem to me like "Hangouts" should be its own thing, along with chat and VoIP. If anything, those things should should sooner be integrated into Gmail somehow. I'm not sure I want that, but it would make more sense, at least, since it's all, roughly speaking, private communications.
I also think that there should be a separate web application that is, "Where my phone automatically uploads my photos, where I can organize them and track them myself, but they're private." Personally, it just makes me a little uncomfortable for that to be bolted straight on to the "photo sharing social networking site," but maybe that's just me. I'm old. I feel ok if the social networking site can connect in and pull photos from the private site. Hell, even if I know it's all ultimately stored in the database, that's not what bothers me. It's just to have my private stuff be in the same interface as the publicly shared stuff, without a clear apparent distinction... it worries my poor little monkey brain.
Ultimately, between Facebook, Twitter, and Google+, I tend to use Facebook for sharing posts/photos/updates. Not because I like it or think it's good, and only somewhat because my friends seem to use it more. As much as anything, I think it's because it's the site that confuses me the least.