I love Christmas at Disney. It's such a blast being with all those people. And that's ironic coming from an extreme introvert.
Get your ADRs and FPs done early, because once the 180 day mark for ADRs and 60 days for FPs breaks, supply will dwindle very quickly. Pretty soon, all you'll find is a 10:30 reservation for Liberty Tree Tavern, Fastpasses for Barnstormer and Small World, and not much else.
Yes, it's nuts. No, you're not riding many rides. The crowd calendars will say that almost every day, every park will be at least a 9. Most of the crowds will be a 10, which is like a sardine moving in a can. On Christmas Day and New Year's Eve, expect MK to go all the way to 11! Each day has a threat of the park entrances closing due to crowds, but 12/25 and 12/31 are the most likely. When we went to MK on 12/31/14, they were bringing the Level 1 closure signs out at 10:00, with talk that they might have to flip it to level 2 as the signs were getting placed.
Wait times are long. Most of the E-ticket rides are at 120-150 minutes all day. The not-so-E-ticket rides were sitting at 90-120 minutes. Stitch's Great Escape once had a posted time of 60 minutes! Who waits an hour for that?
So why do I love Christmas? I don't know. I think it's just wanting to spend the end of the year with probably, what, maybe 200,000 or so people? I just love watching all the smiles, and all the cheer, knowing you'll be at the best fireworks show to end the calendar, anywhere. It's the laughter and the camaraderie. It's being with people who are thankful for what the last year had brought, and looking forward to what the next year will bring.
It's the decorations, it's the extra touches that everything gets. The lights, the music, the vibe. It's unique to Christmas.
There's special events all over. At Epcot, if you want to do things like the Candlelight Processional at Epcot, make sure to book a package which includes a meal. They also give you tickets good for one show that day, the show time will be on the ticket. Without that, the standby line can be hours, with no guarantee you'll get a seat. At the Magic Kingdom, you may have to stake your spot for the fireworks early. Some people start as early as noon. I did the dessert party on New Year's Eve, and it was fantastic! We had our own spot to see Holiday Wishes, and we didn't have to stand still for 12 hours.
But in a nutshell, keep your expectations low. Find things off the beaten path. Know that getting from point A to point B will be a little more difficult. TS restaurants may be backed up, no, they will be backed up. Lines for everything from cashing in Fastpasses, to getting a cheeseburger, to getting on a bus, will all take more time than normal. Keep that in mind, and everything will be a perk.
Even with all the crowds and all the celebrations, one of my best times was in a quiet pool at POR, at the end of New Year's Day, by myself. Me, my thoughts, and a little puddle of water at Walt Disney World. I had the hotel room smelling like chlorine when I went back in, and it bothered my family. I loved it!
But if it's one thing I implore you to bring to this trip, it's patience.