I went last Thanksgiving. I actually planned the trip Friday and left Sunday. LOL We checked in the Sunday before Thanksgiving and checked out Friday after Thanksgiving. We followed TGM and had a GREAT time. Wednesday at MK was amazing! It was raining most of the day, we got there at RD, left around 1:30, and came back around 5:30 (just as the rain stopped) and stayed until they closed. It was not crowded at all. It was a little cool but I'll take that over the summer heat any day! We went to AK on Thanksgiving day and it wasn't bad at all.
There were a ton of people checking in on Wednesday and I would say that was when the crowds picked up at the hotel (AKL) but overall nothing was bad. At Epcot, we rode TT like 6 times, MS about 7 times and Soarin' twice. At MK, we rode SM 3 times (it broke down), SM and BTM about 5 times. I would definitely go back that week again. We expected crowds, utilized RD, take breaks and went back at night. I went because I wanted to see the Christmas lights and decorations. Seeing the castle covered in those beautiful lights was truly magical. Soooo beautiful.
IT was packed. So we now leave for home on Friday. We like arriving the week before so that we get a lot done RIDE WISE before say Tuesday when it starts getting more crowded. You will want to follow TGM for sure. 
going at Thanksgiving...just a beautiful time with all of the Christmas decorations. I don't think you will be disappointed at all. There is just a holiday feeling in the air that just makes the time spent there truly magical. We have been able to attend the MVMCP twice on these trips. There is usually one on Thursday or Friday before Thanksgiving.
