I go to either Universal or Disney almost every year during that week. The crowds are very light, but the weather is inconsistent. There have been years where we wore shorts and years that we had to go out and buy turtlenecks, fleece pullovers and gloves and we almost always have at least a couple of days of rain in the morning so bring the ponchos! (Don't buy them in the parks!) However, for us, it's been a good trade off for the lack of lines to get on the rides and attractions. We also love the feel of Christmas with all of the decorations and music!