We went to Disney World over the holidays. We were nervous as we had read online that this can be the most crowded time of the year. It was indeed crowded but doable. We went to Epcot on Christmas Day which I think is the best park to go to on Christmas as Epcot can handle the bigger crowds. I never felt overwhelmed there except around 7:30 p.m. that evening when a traffic jam of people on a narrower walkway near the Middle East land occurred. It also got a little too congested in Norway which also has narrower walkways.
Disney is always a class act and what was very impressive was how clean it was at the busiest time of the year. When we were at Epcot I was able to speak with one of the janitors and she said that they had at least 250 to 300 cleaners working in EACH section of Epcot that day. They did a great job on Christmas and helped provide wonderful memories for our family.