We've gone to WDW 38 visits with a coupple in December, firts and second week only. Crowds were non existent, great time to go. weather is a big issue, we're from northeast Ohio, and we wanted to escape the winter snows and cold. Florida can be unpredicable. One year they were having a freak break and the temps were in the high 80's, great, swimming weather in December, loved it, then again the next December trip, we needed soats, really cold, made your nose run, not alot of fun.
I found out to get the best of both worlds, October or early November, xmas stuff is up, weather is alot better, predictable and crowds on the down side but then again, WDW is so unpredictable, you never know whats going on, guess you just pick you time and live with the outcome. Even if there are crowds, we still can cruise and enjoy the parks, its Disney and just being there in Florida is half the fun.