If you are asking about the crowds Thanksgiving is the second busiest week behind Christmas.
If you go the week before Thanksgiving then you will be pleasantly surprised, the crowds are very low and you will able to move about with ease not to mention that the wait times are next to none!
We went in '06 the week before and the wait time for Soarin' was 10 mins on the day we arrived (11-15) Wednesday, by the following Monday the wait time was 120 mins, just to give you an idea.
We have gone the last 2 years @ Thanksgiving and once a couple years ago. Very busy Wed- Sat, not so much before. Still not as bad as April, I think. Maybe because it is cooler. Have dinner on turkey day at liberty Tree tavern in MK!