We were a little nervous about going in October after having been the week after Thanksgiving. We were worried about bigger crowds, heat, etc... We went Oct. 2-9 last fall and it was perfect!!! We were in the MK by 1pm the Saturday we arrived. We were amazed at how much we were able to do when we were just getting there at the time most people on these boards advise going back to the room to avoid the crowds. It wasn't empty, and we did use FastPass some, but we did everything in Tomorrowland, ToonTown, and Fantasyland that afternoon. Then, we saw Spectromagic and Wishes that night. It was awesome. By Monday morning, there were even fewer people. We never waited in line more than 10-15 minutes for anything in any park. We didn't even need FastPass most of the time. Crowds did pick up by Thursday of that week before Columbus Day weekend. We had "done" the parks by then, and just used that last bit to rest and do water parks.
We aren't going to be able to go back this year. :-( But we do plan to go during Oct next year! It works well to go during our school's fall break.