We went December 10th to 19 this past year. We felt it was unusually crowded, especially in TSL or Pandora, as was to be expected. We were glad we had our 3 fp's because some wait times were too long for us. If you plan to Not go to the popular rides first thing, you will have a better chance of riding other rides. For example: At the MK at rope drop: While everyone else headed to 7dmt and fantasyland, we went to adventure land and had walk on's for BTMRR and POC. It was great. However, fantasyland was super busy whenever we went. At the AK, while everyone went to Pandora, we went to EE, Dinosaur, etc and had no waits. It can be done with fp's for FOP and SDD, and avoiding the busiest places while riding the other rides. That worked for us.
This time of year used to be slower, but not any more. We just adjusted our touring style, but we probably won't be back during this time again.