I just got back and I thought crowds were incrediby good (but I've been three other times in my life, and two were during spring break and one was a school band trip in the end of May so those were probably really busy times. Dec. 12 was our first day and we walked onto everything in MK. I agree with a previous poster, I think the listed wait times were deceptive, Space Mt. said 15 minutes and we walked right on. Our only crowded day was Epcot on Friday, which I think is understandable because it was a weekend and an extra magic hours night. We got fastpasses for Soarin three times and were on the ride within 10 minutes of our time coming up.
I loved this time of year, even though I have never been in early December before so I can't compare it to other times. All I know is what I experienced and I really don't mind waiting 10-20 minutes for bigger name attractions like Soarin (with a fast pass of course). Great decorations, great weather (cept for Monday), great experience.