I did a Thanksgiving trip in 2004. We arrived the Sunday before Thanksgiving and left the Sunday after. The crowds were light to moderate up to Thursday, then definitely heavy, but not unbearable Friday, Saturday and Sunday. The holiday decorations were up already when we arrived. We had our holiday meal at the Yachtsman. The weather was very pleasant. It was a great time to visit.
They used to say that the first 2 weeks of December were really light as far as the crowds go, but I think this year was an exception (if I remember what I've read about trips from that time correctly).