I have a boxer puppy, this will be my third one.
I live by a big off-leash area and I see Pitbulls all the time. They play with all the other dogs. They are great dogs, I find alot of them to be very submissive.
In fact, I have never seen an aggressive Pitbull. My cousin had one named Razor, the sweetest little guy you could ever meet.
I have seen far more aggressive Border Collies, Huskies, Poodles and cross breeds at the dog park. My last boxer who passed away was bitten by a Collie on the butt as my dog was walking away. My boxer just ran off and tried to get away from that dog.
I think Pitbulls are very trainable and there is one that is at the park every night that catches frisbee and is one of my favourite dogs at the park. I have never encountered a single problem with a Pitbull.