I've had a couple meals at The Top of the Port which is located outside security at the top of the hotel in Terminal E. It isn't fantastic (certainly not worth a comparison to OFS), but I think it's the best option for a sit-down meal out of the hustle and bustle of the terminal. The food options at MIA are pretty limited.
I've never tried to venture off airport property for a meal. I can tell you there's great food in Miami proper, but I'm not familiar enough with the area around MIA to be of any use. You might try the AA forum for advice on all things MIA.
*And I certainly wouldn't extend a layover just to eat there... but if stuck with one of those awkward layovers that's too short to leave but too long to just sit around, I think it's a decent option.