In general I like it and I've got back in touch with a few people from college/school there. I have pretty much the highest security level possible - only friends of friends can find me and as Zebra says, you can set your photos to be seen by friends only (I do this). I've had some nobbers from school try and add me, but I just ignore them. Fundamentally I'm a very nosy person who wants to know what happened to everyone from school/college!
It's more difficult when a colleague you don't like or want to be associated with, but whom you see regularly, tries to add you. It would be obvious, and this person is gauche enough to bring it up when I see him - any suggestions?