This is one of my favorite pics from my last trip to Disney World. The Christmas decorations look great and it's a great time of year to be in the Parks. The weather is usually really nice and there are even some hot days. I avoid the Disney Park crowds
between Christmas and Easter, spending that week at the beach instead, but the first week of January is excellent.
The early weeks in December are fairly light on crowds and you can enjoy the decorations, so that's a good time to go. If you wait until after New Year's though, Disney World cast members may have pulled down everything before you get a chance to see it. They are fast! They start removing the Christmas decor on January 2nd and a few days later it will be all gone. Osborne Lights now runs a little bit longer --- until about January 7th, but that's about it.