We were also there last year, 12/27 to 1/1. We had a blast. Echo previous post about being prepared for lots of people. Go understanding that you need to plan about meals, use fastpass, and possibly not get to see everything you want, and you will be OK!
You do not mention if you will have kids with you, or their ages. We were fortunate in that DD is 14, and was able to "accept" missing out on a few rides due to lines that were just too long (of course, part of the reason we missed out was because she couldn't get out of bed early enough

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If you have little ones who will be devasted not to ride certain things, then make sure you make those rides a priority, and get to the parks when they open. You should not have too much trouble then.
Be prepared, as already mentioned to get those priority seatings done for major meals. We did counter service early for lunch (11 am, no wait time), and sit down meals each night. Breakfast was in our room, except for one character breakfast on New Years Day. NYE priority seating is a MUST. I was ready to call at exactly 90 days out, was on hold for an hour, but got our seating at Chefs de France. It was a lovely dinner. Even at that, we still waited for our table for about 45 minutes.......and were amazed at the people who walked up that evening, hoping to get in. The maitre'd just shook his head
The Candlelight processional went until 12/30: don't miss it!

The Osbourne lights at MGM were also magnificent. See them at the end of the evening, after the initial "crush" of people have passed. We went around 10, and no one was there. It was great.
Let me know if you have any other questions, and have fun planning! Wish we were going to be there with you!
