We were there from the 16th - the 21st of December this past season, I wouldn't go back again during that time. Too crowded for me. When we got there on Thurs. it wasn't bad, Friday got a bit busier but by Sat (an entire week before Xmas) it was way too busy for me.
We have the luxury of going a few times a year so we do prefer to go during off peak times. We usually go in early Dec. but this year decided to try later in the month but definitely prefer early December.
I guess it's all "relative" as far as when you can go and when you normally go on what you compare the crowds with, but for example after Friday we couldn't even get FPs to Soarin anytime of the day. Standby times were 3 hrs by noon.