...in 1999, from Dec 12-21.
Crowds were excellent -- which is to say, very low. Many big attractions were walk-ons, or had less than 15 minute waits.
Weather is nice, too -- a little chilly in the morning and evening, but pleasantly warm the rest of the day. Bring a sweater or jacket and long pants. Sometimes, the temps can dip into the 30s!
Anyone in The World during the holiday season should try
MVMCP at least once. (For the record: we weren't that thrilled with it, but it seems were are in the minority. The snow on Main Street and the hot chocolate were great, though!)
If you can, take an afternoon just to visit some of the resorts and gawk at the trees. (The GF and WL are tops, IMHO!). The decorations are truly beautiful, all over The World, and you can't help but catch the Christmas spirit!
And in Epcot, there are international Santas strolling the World Showcase: Kringles and such representing the different cultures of each country, and telling stories of their homeland traditions. Very cool.