I was there Dec. 2-6, and did find it much busier than my last early December trip back in 2000. The crowds weren't unbearable, but there were some longer waits than I'm used to, and the All-Star resorts were packed with kids. I was glad that I rented a car, which I used the entire trip to go back and forth to the parks.
I always go during the "slow" seasons, and was just there for a week in September, where I practically walked on everything, so this trip I just took my time and didn't feel that I had to do and see everything. I actually took the time to do some shows and attractions that I haven't done in years, like "Beauty and the Beast", which was wonderful.
I saw all the movies in World Showcase, including Norway!
The lines for the Candlelight Procession seemed to stretch for miles

, so I ended up watching it from the back, which was still thrilling and emotional. Saturday night, the wait for It's a Small World was 60 minutes!
I really think it's all relative as to what you think is crowded. If you normally go during the crowded summer months, then you would love the lighter crowds, whereas if you are used to the quietest times, then it was a little bit busier for you.