Facebook is not accessible from work, so don't expect anything timely from it.
On first impression, I find Facebook is noisy, and gives the illusion of connectedness. Get enough people with your fiends, and it feels like the buzz in a room.
At the moment, I far prefer LJ.
I'll reserve Facebook for people from the material world. I don't remember who else used that as their controlling factor for FB, but I like it, so I'm adopting it.
I'll be insecure and add anyone who wants, just to prove that I have friends and that people actually like me.