We landed on the 3rd this year. As Lancashirefatcat said the weather was really good. A lot less rain than we expected and very very hot. We had a really odd day on the last Sunday before we came back - sort of really cloudy and windy and drizzly. But, because the area is so vast you can literally be in rain and thunderstorms in Kissimmee but in glorious sunshine at the Magic Kingdom! One of the locals (ex pat) told us that the Disney site alone is the size of Manchester! It's hard to get your head 'round! We were glad of the rain some days as it was so hot. It doesn't last long and the thunderstorms are really quite exciting. If it rains and you have a car then you can always pop off and do some shopping!
Parks were really quiet which was great. No over crowding or long que's. The que's we did have to wait in we're 15 mins max. Perfect really.
The let down for me was the 'Dreamliner' bit though. We had problems coming home (they're still having a few teething issues I think) so no inflight entertainment for me! Bit of a nightmare because this console controls the light above your head too so I couldn't even read a book! Long long flight home twiddling my thumbs in the dark! Three hours late leaving, dirty cabin/seats, awful food etc etc! I wasn't calling it the 'Dream'liner that day I can tell you! But I was just unlucky.
Anyway, we lliked September so much we booked our accommodation for next year while we were there! At this year's rates!
You'll have a brilliant time. Go out and explore too. Orlando's fab!!