We've visited the first week in December and during the Food and Wine festival and found both to be reasonable for ride lines. We always get to the park at opening and go on rides first (don't stop for characters, food, etc). We usually get to ride 5 to 10 rides in the first two hours. Then we take some character or food breaks. We head by to the resort in the afternoon for naps and swimming and go back at night for "some" rides. We plan that there will be lines at night and there are. We also plan two days for each park, pretty much going to different rides each day so we can see everything with out too much wait.
I know some will say that early December is getting way more crowded but we simply didn't find that to be true. I'm sure its more crowded than years past, but its really not that bad