We spent this past NYE at Epcot. I was prepared for wall to wall people and being stuck in one place. It really wasn't like that at all. Some areas were congested but the bypasses were open to allow you to move around. I really enjoyed it and would love to go back without my family since they were holding me back - lol! We found a fireworks spot maybe 30 minutes before the show with no issues. Many people were desperately trying to squeeze in at the last minute and being chased off by the CMs.
I definitely recommend having a dinner reservation somewhere. We went to Via Napoli, which was great, but the music in the Italy pavilion was incredibly loud and could not be escaped even inside the restaurant. I think I'd chose a different country next time for that reason.
Be prepared to wait a very long time for a bus. We were staying at Saratoga Springs and waited over an hour for a bus, after killing a bunch of time in World Showcase. I think we got back to our room around 3:30 or so.