It used to be much more fun years ago, but it's changed so many times now, sometimes for the better and sometimes for the worse.
I find it good for keeping in touch with people and for social stuff, it's great for keeping abreast of what's going on in your locale. I get on guests lists and invites to all kinds of events, gigs, club nights et.c. through FB. It's still has that stalkerish edge which is weird because it makes almost everyone on it into a cyber-stalker. I love looking at people's photos and FB really is good for reuniting you with people you haven't spoken to in years, though whether you actually end up rekindling your friendship is another matter. My family are crap at keeping in touch with eachother so it's useful for keeping that connection up.
But it really isn't as much fun as it used to be.