I fly quite frequently from Orlando via Miami with AA and never missed a connection. I usually have a hour and half to kill in Miami, every now and then the flight to BZ is delayed but don't count on it for adding time in making your connection.
I also travel light and don't check any luggage in. lost it once going to another destination. what a pain!
find out before hand what gates you'll be arriving and departing from and get there ASAP - MIA is a rat race - lotsa construction! the security check times and lines aren't too bad though.