Well, I used the lounge on Saturday night and was generally unimpressed.
Self serve drinks are a bonus, the food offering was mediocre (but better than many other lounges I guess). The preceding flight was delayed so the lounge was very busy and we (a group of 5) struggled to find a place to sit. Oh, and there's only one elevator working at the moment, resulting in long queues when they do call a flight.
On the plus side they did have two TV rooms, one of which had cartoons on - very sensible given it was Florida at the end of the Easter break.
On a side note, it seems that no one at BA bothered to tell MIA about the new late departure - when we walked through the E gates about 9.45pm, all the service offerings were closed up for the night.