I'm on Google+. Overall, I would say it's the first social networking tool that seems to have actually tried to ask "what do people want/need in a social networking tool?" I'm also hoping they leave it really bare bones and let people add to it via gadgets, like how you currently add features to gmail by selecting which features you like in Labs. As more of my friends get Google+ accounts, I will be looking to phase out my use of Facebook.
The only thing I find a little unnerving is using Google for so many things - docs, email, social networking, browser, etc.