i personally hate what FB has become. i joined in '03 when a university e-mail was a requirement and there was not a news feed, ad, or game in sight. i don't want people to take this the wrong way, but opening it to everyone seriously dumbed the whole place down. combine that with the constant "updates" that seem to make the site more annoying every time i log on, and i really wish i could leave. the only reason i still use it is because very few of my friends have moved to another service.
twitter is my social network of choice at the moment. i love the light hearted atmosphere, and the fact that it is not nearly as commercialized as any other social networking site. i don't have many followers over there, but it is definitely the most fun, IMO.
G+ seems like it could be nice, but i personally only know 5-10 other people that are on it, in comparison to the 500+ i have on FB. i feel like posting anything over there is just going through the motions since no one i know is going to see it anyway.