Is a American Bulldog a good first time dog?

I do have a bit of expirence with dogs, all my cousins have mastiffs and I would take care and walk them sometimes, i would really like this dog only thing that scares me is its bite force round 300 pounds but dogs dont attack unless provoked but none the less im not scared of dogs in general or anything, i do have the time and will exercise it regularly, i would like to hear the people who own this dog and tell me there own personal expirence about this dog.