We were there the 17th-24th in December and it was the best trip we have ever had. Crowd wise, everyone is correct that it somewhat builds leading up to Christmas but we literally rode every ride there, many multiple times, (including Flight of Passage three times in ONE DAY) and never waited more than 15-20 min utilizing fast pass, additional same day fast pass, single rider, and rope drop. The only real issue where crowds affected was on non party days, watching Happily Ever After fireworks. That was INSANE as far as crowds. But to us time is money so for that I did spring for the dessert party since that was a priority for us for this trip. We did the Christmas party and that to was worth it to us to have a evening of little wait times for the rides and the atmosphere. We were there early morning, often with pre park opening breakfasts which helped. had our lunches scheduled for around 1:00 or so, took a two hour or so break, then back to the parks for as late as we could stay. When the crowds got kinda crazy and we didnt have a fast pass for something we would do the rides/shows such as people mover, philharmagic, World Showcase, Nemo Show, Lion King Shows things like that in the afternoon busier times and then hit the most popular rides early morning, with a fast pass, or late evening. With planning and a strategy it was awesome and every day in every park we were in was an 8 or 9 out of 10.