As far as limiting what you see... I have a number of "friends" for actual networking reasons who annoy me so much that I hide any feed from them. I think you can set up groups now, too, so that your posts won't show up on everyone's wall, just select people?

I use Facebook mostly to keep in touch with my younger sister (she, for some reason, only owns a cordful phone - as she puts it - and therefore won't talk on it, so we chat online instead). I have a few other friends that I live halfway across the country from and it's useful in keeping up with them, and for looking at the gazillion photos of all of my friends' babies and toddlers. It's definitely a huge timesuck if you allow it, though!