I met regular sized american bully while on a walk this evening, first time seeing one in person. Looks and behaves like any bully breed, a 3 year old in a muscle suit that could crush bricks. Definitely needs proper training by an owner but I wouldn't say it's that different from English bullterrier.
Bad rep for those dogs is mostly the looks. I own a bullterrier who made some people nervous / scared despite being a dumb but well behaved goofball. This changed almost immediately after one of his ears flopped due to a blood clot. I often joke that he lost all of the street cred and gets no respect.