If you are familiar with the parks and what you want to go on you should have no problem. We were there this last Christmas and I thought it was less busy than previous holiday trips. Just plan on being at the park before opening time, head straight to the most popular rides, use fastpass for others and keep moving from ride to ride. We (3 adults one young child) covered everything we wanted to ride by mid morning, took a nap, returned to parks for shows/parades etc in the pm. Stay onsite, use busses and extended hours. Mornings were great for the rides, evenings were good for shows, except for Animal Kingdom where Dinosaur was walk on one night right at normal park closing and I went on it 3X as fast as you could walk around front to get back in. Here's an example of what we did the am of Dec 24th. Space Mtn, Buzz 2X, Indy Speedway, Pooh, Philharmagic, Peter Pan, Snow White, Small World, Haunted Mansion, Big Thunder 2X, Pirates, Jungle Cruise and at least a half dozen photo's w/characters. I don't recall what time we were done, but it was well before noon and I remember thinking the morning wasn't even over and we were leaving to head back to the resort for a break. One advantage of going during the busy season is the rides are normally running at full capacity right away in the morning so it will save you even more time. Space and Big Thunder had both sides running and moving the people through as fast as they came in.