Your experience really depends on your group's comfort level with crowds. Everywhere you go, from restrooms to restaurants to shops to restaurants to rides to even the tiniest corridors, are beyond packed, but if you've never felt extremely bothered by crowds, you'll have a great time. Crowds don't really get to me, so I had a blast on NYE. If you go for the experience and not for the rides, you won't be disappointed. The holiday decorations are, of course, still there, plus the atmosphere is really any other day, it would drive me bananas, but I found it to be fun and festive. They've got
Went this past NYE to MK and had a blast. I really managed expectations when it comes to rides for that day and made it kind of a low priority for me. Of course, I still made FP+s and got on a number of rides with my longest wait being 35 mins for PotC I think. How I did it was we decided, because we were going to be up late, to sleep in and do a 10:30 breakfast at Chef Mickey's before heading into the parks. We had FP+s that afternoon for Space, Splash, and 7DMT. According to
MDE, we also scored additional passes for BTMRR, Buzz, and Peter Pan. I thought it was particularly cool how MK did two sets of fireworks that night. We saw the 7:30 Holiday Wishes from the back of MSUSA and then bee-lined it to the bus to YC to meet the saner half of our party (who chose to spend the day relaxing at our hotel, the Dolphin) for dinner at Yachtsman Steakhouse at 8:30. They brought us a change of clothes and we had a nice relaxing meal and head out at about 11 to go back to MK, while they had desserts and chatted. It was tight but we made it and got a decent view of the fireworks towards the end of MSUSA. We did a few more rides before the park closed at 1. Yeah, we were exhausted and there were certainly parts of the day that were very stressful (mainly the leaving for Yachtsman and getting back in time for fireworks), but looking back on it, it was a lot of fun.
If you go for the experience and not for the rides, you won't be disappointed. The holiday decorations are, of course, still there, plus the atmosphere is really exciting. Starting at about 4pm, they'll be handing out hats and horns for free, so from that point on, everyone's going around the park blowing their horns. On any other day, it would drive me bananas, but I found it to be fun and festive. They've got upbeat, pop music playing throughout the park at night too. Like others have said, MK is very family-friendly for NYE, but sometime, I'd like to try Epcot's NYE. I've also heard the Fantasia dinner is great fun there, and you get the added bonus of reserved seating for IllumiNations. I believe bookings for that open within the next month.
Also, just a little known tip, the restaurants do not charge no-show fees on NYE due to the crowding and capacity closures, so if you're feeling like it's too much and you won't make it to dinner, that's fine. Obviously, if you know in advance that you're not going to show, cancel the ADR, but if you're unsure, you won't be charged.