We flew in April and it was a full flight not one empty seat. But it wasn't overbooked.... I have heard of them over booking but, I haven't had a problem with them.
I would think it would depend on:
-where the flight is from
-how often their are flights to mco from that destination
-if its school vacation
-day of the week
Yet, one more reason to get to the airport early! cant understand why people continue to arrive much later than the suggested arrival time at the airport then can't figure out why their "reserved" seat has been given away. Alot of airlines overbook.... we fly alot and have never had a problem with AirTran or any other airlines.