I know this was a long time ago but we went Dec 17-23 in 2000 for our honeymoon and I would do it again in a minute! There were virtually no crowds, I think the longest we waited in line was 10 minutes. It was great seeing everything decorated for Christmas, and the Osbourne Lights were awesome! Some days weather was great...light jacket was fine but most of the trip they just happened to have record low temps. We of course being from NJ never expected FL to be like that so we weren't prepared and had to buy hats, gloves, and scarves. It was kind of comical...every store had giant boxes of winter wear in their doorways since a lot of people had the same thoughts as us (it's FL, why would we need snowwear?)
We froze our butts off playing golf at night and got a free round out of it since we were the only crazy fools out there playing!
It was a lot of fun...just be prepared for anything! Make sure you watch the weather reports before you go!