We were there Christmas week and also Easter week. It is essential to get to the parks early enough to be at the front of rope drop. You also never know when parks will actually open. We were there two weeks ago, and EP, HS and AK opened about 20 minutes early.
During our day over Christmas break, they upset our plans by adding an EMH (we weren't resort guests). We still planned to arrive 1/2 hour before the EMH started, so that we could get "in line". I wasn't sure what to expect. We got there so early we beat the parking attendants! I was shocked when they let us in with the EMH guests! So, my early-bird plan worked out extremely well
Between 7-11, we were able to ride/see 16 attractions! Around 11, it got really crowded: So crowded you couldn't navigate the park well at all. We planned our Crystal Palace meal at 1:40, which was the perfect time for a long break to get out of the crowds.
As expected, they did enforce closures due to being at capacity, so don't plan to leave and come back. They won't necessarily let you in, even if you have fast passes or a dining reservation.
I went in to all of this expecting the entire day to be so crowded we couldn't walk. Those early hours were so nice, and we got so much done! Yes, it eventually got as crowded as I expected, but we had already done what we wanted to do!