Just got home from a Christmas week trip! As for NYE specifically, my group of 5 headed to Epcot around 10 pm. Stayed at the Swan so it was an easy walk! No issues or lines getting in at the International Gateway entrance.
Once there, the atmosphere was great- full on dance parties in China, Japan, and Italy complete with lasers and even pyrotechnics. There was a bar or pop up bar frequently around the World Showcase so if you're interested, drinks were easy to find (but lines were long.) Overall, it was super crowded, but CMs kept the traffic moving and the ground was taped out with walking lanes and sitting areas. Everyone was in great spirits and I didn't find too many obnoxiously drink people.
As far as fireworks, we finally decided on a spot around 11:10 as they start Illuminations at 11:40. We found a spot behind bushes in Japan which wasn't an ideal spot, but completely fine and not crowded around us. I'd recommend picking a spot and sitting no later than when we did as areas got full and you had to be in a taped off sitting/ viewing area. (Alternatively, you could be one of the people that we saw camping out around noon earlier in the day when we headed over to get lunch. Unless you have Fastpasses, I wouldn't recommend counting on rides that day- lines were insane.)
Fireworks were amazing (illuminations plus the NYE add on) and the finale was one of the most memorable things I've ever seen. They also recognized the countries who had celebrated the New Year earlier in the day with individual fireworks. Highly recommended!
New Year's Day found Epcot noticeably less crowded- it was SO nice comparatively to earlier that week. Easily able to use our fast passes and find seating for lunch before heading to the airport. Have to say that we talked about arriving the 30th for future trips and staying the week after based on the lowerish crowds.
Hope this helps a bit!
