Check Travel Net and see how many flights per day there are, and which equipment type is on it, you can also see how overbooked each flight is. In the winter of course it's a lot busier than in August, but MCO seems to fill up every flight, every day, every month.

September is Disney's slowest month, but MCO also is the place the Port Canaveral cruise ship people fly in/out of, so there's that too. Delta has been replacing some of the 757's with 737's and MD88's in MCO, so watch out. Over Spring Break last month they did put some 767-300's on instead of 757's, which was nice, but I still had to sit in the jump seat both ways, back was completely full.