It's our favorite time to go. I honestly don't think in 2 trips at that time of the year we waited more than 20 minutes for anything (and that was Everest in its first year).
The weather is wonderful. I usually layer and find that works well. I usually go with a tshirt, jacket, and capris.
All of the decorations are up, so you get to experience the Christmas season without the crowds and for a lot less money.