We also rode Nemo during Early Entry (our trip was in August). We were at the gates by 6:45 a.m. and there was already a large group of people waiting to get in. At 7:00 a.m. they started letting people in and nearly everyone headed toward Nemo. We walked quickly and got in line right away. It took us 30 minutes to reach the front of the line and board the ride. The rest of the day, the wait never went below 90 minutes and was often well over 2 hours so we were glad we went early. We stayed until midnight twice and the line was still well over an hour even that late.
If you're getting at least a 3 day pass, you'll be eligible for Early Entry on one day. I would recommend getting there before 7:00 a.m. and riding Nemo first thing. It's really early, but it's worth it. After Nemo, we were able to do a bunch of Fantasyland rides before the park got too crowded. Most rides didn't have lines until after 9:00 a.m.