We were there in 2008 from the Saturday before Thanksgiving until the Saturday after. The first few days were ok, comparable to what I have seen in early June, got busier each day until Thursday (Thanksgiving), and from Thanksgiving Day on, it was BUSY. We were at Epcot on Friday (the day after Thanksgiving) and the boat captain said there were 40,000 people in Epcot right then. I don't know if that is a lot attendance-wise, but I do know IT WAS PACKED ALL DAY. We did Animal Kingdom on Sat and had done Magic Kingdom on Thanksgiving Day. I have never seen so many people in the parks as I did on those three days. Ugghh! We still had a good time though, and it was great to get to see all of the Christmas decorations. It was our first time seeing the Santa's Around the World and the Candlelight Processional. Just don't expect to accomplish a whole lot Thurs, Fri and Sat. If you are having to chose a time when school is out, then yes, I would choose Thanksgiving week instead of during Christmas break. Hope that helps!