definitely the earlier the better as they will close the park when it gets full to capacity. think we got in about 8ish am and stayed to see the New Year in. great fun and can highly recommend it. It is a long day but if you pace yourself you should be fine. Dont expect to get on too many rides as times are horrendous but lots of other things to keep you entertained.
We get there for just before opening time. 1st time we arrived at 9:30am to be told it was closed to offsite guests, they were reaching capacity, thankfully we were staying onsite so they let us in. other 4 visits on NYE we got there early. I have heard of people getting in later but its very hit or miss. Many people leave after the 1st lot of fireworks around 8pm, we have never stayed for the 2nd lot, NY to us is 7pm (12 midnight UK)
As above the rides lines are crazy, you will struggle to do any. This shows Soarin at almost 5 hours, I heard later in the day it reached 7 hours.
because the parks are so busy we usualy have a rest day ( have done DC that day but brrrrr). The have dinner at the poly and watch the new year fireworks from the poly beach - they actually do a numerical firework count down in the sky- they are deff the best fireworkd we have ever seen- anywhere.
There is a DJ and dance music at Atlantic Dance Hall on New Years Eve as well. It has been known some years to sell out in advance. Tickets go on sale a few days after Christmas.
We watched the fireworks from the Poly beach, they are the most amazing fireworks i've ever seen. They also set them off on the 30th if you want to do something else on the 31st.