We went from Dec. 26th through Jan. 4th in 2013. For being the busiest time of the year, I thought it was manageable with a little planning.
Here are some suggestions of what we did:
We pretty much made rope drop every morning (aside from NYE - we slept in and made alternate plans). If you really want to make some breakfast reservations, I suggest getting to the parks early, riding a few rides, then eating. At Animal Kingdom we rode, Everest, Dinosaur and that spinning coaster then went to check in for our breakfast reservation at 10:30. We rode safari right after breakfast, did some other stuff, saw Nemo show and then we were done by mid afternoon.
UP until the 30th, I though crowds were manageable. But the crowds on the 30th were huge. We happened to be at Hollywood Studios that day. For HS, I would suggest seeing the first Fantasmic Show. They open up early and you can go in and wait in your seats. They have a dj and try to do some fun things while you wait. Much more relaxing then when we came out and the line to get in for the 2nd show was to the front of the park by the entrance. After Fantasmic we did the Osborne Lights. Only two rides we did at night were TOT and Toy Story. We rode everything else before the Fantasmic show.
We decided to go to Downtown Disney on NYE after some mini golfing. The parks that day were at capacity by 9:30 in the morning and we saw on the news the lines at MK were 5 hour waits. Craziness.
For Magic Kingdom, we went at least 2 days there. I suggest starting in a different area each day - be strategic when making your fast pass reservations.
Make time to look at all the lights, decorations at different resorts etc. It's part of the fun and atmosphere.