Ah, dogchat :)
I'm pretty into animal related things--I'm studying to be a vet tech and I volunteer at a local SPCA.
A lot of the dogs that come in are, unsurprisingly, Pitbulls and American Staffordshire terriers (a similar breed that usually gets lumped in with pitties).
Each dog has its own personality...and some breeds tend more towards a certain personality type. I'd say most of the pitbulls/amstaffs I have met are rather energetic and friendly dogs.
But they are EXTREMELY powerful. They're stout, heavily muscled, and built like tanks, with massive heads and jaws. If they're poorly trained, it's a disaster. They'll pull your arm out of its socket on a walk, bowl you over when they're happy to see you (which is usually), if they get too excited and play rough they can seriously hurt you, and getting whapped by their wagging tail is pretty ouchy, too.
Truthfully, of all the puppies that come in, in my experience pitties/amstaffs are the worst. They're strong, stubborn, and they REALLY like to nip. They're like little alligators, and they have excellent instincts for biting weak spots. When they play with other dogs, they immediately go for the loose throat skin, and they latch on good.
But gosh, they can grow up to be so nice. If you train them well and don't encourage bad behavoir, good golly are they sweet doggies. And they really love their people, so they're good learners :)
Of course, with any dog, and any human if you think about it, there will always be circumstances under which they will feel pressured to attack, but...that's just natural.
Ehehe. I'm not any kind of expert, but I guess those are my experiences.