AA are a decent enough airline. I haven't flown with them to Miami, but I have to Chicago and NY, and the planes were modern, with seatback tv's etc. Our last flight with them was last February, and they still had the extra pitch then (it's a few inches in front, but that didn't half make a difference to the feeling of space all around you) - I know they were scaling this back, but I don't know whether this is now fully completed.
The inflight movies were good - and because it's an American airline, they were even newer films than say BA or Virgin. Food was just as you expect on an aeroplane, and like most, if not all, American airlines, you do pay for alcohol ($5 per drink, soft drinks are free).
Your flight between Miami and Orlando may well be on a much smaller plane, with no tv etc, but that flight should only be an hour or so.
One thing I do know about Miami International is that it's not the nicest airport in the world - it is huge, and needs updating, although that may have been done in the past couple of years - and it's busy busy busy. It just seems less organised than other US airports somehow, buat least you can clear customs here, and it's usually straightforward to recheck your bags - you are usually checked straight through if it's the same airline, so you just collect your bags, and then put them on another carousel, and go straight to your gate.
I wouldn't hesitate to travel indirectly if the savings were substantial. It's really no big deal.
Hope that helps
