The pit bulls that we've owned or helped train are very friendly with people. Altho I personally prefer Lab-mixes, I believe that pits are a little better with people, tougher to benign abuse, and a little more cuddly. Very strong dogs with a love of tug. I consider them to be a little more energetic than Labs, a little less easy to train... but still easy to train, and quicker, with faster reflexes.
I believe that a socialized pit will not be aggressive, but also will not back down if another dog growls.
I think that one source of the bad reputation comes from over-excitement. We helped one family train an amazingly sweet female pit with Bite Inhibition that was soft as cotton. On the other hand, my nephew has a pit with inadequate Bite Inhibition that can draw blood while playing with other dogs, and can nip people during tug .... not aggression by any stretch, just over-excitement and inadequate Bite Inhibition. I have minimal control over the training, and I'm not allowed to use a newspaper on my nephew :-)