I also love Christmas time at WDW. I've been several times, most recently the first week of December 2007, and my wife and I both really like it a lot. The decorations, music, and the special shows and parties really make a good vacation even better.
I'd be prepared for a wide range of weather. It can go from warm to cold rather quickly, and it always seems extra windy on the cold days.
Sadly, I really can't say that early December is as uncrowded as it used to be. There were consistantly large crowds the whole week we were there, especially for transportation. I think this is more proof that there really aren't as many "slow times" as there used to be at WDW.