It's good for keeping in touch with people who live far from you - Though I feel people tend to rely on it too much as a tool for maintaining friendships, rather than visiting those friends face to face and talking to/doing stuff with them. Bit sad to see really.
I stopped really checking mine. Half my friends on there either don't do anything interesting enough for me to comment on (and vice versa with me for them, I guess
) or have most of their posts in a language that I can't speak well enough to respond with what I'd want to.