Went on the Friday before Halloween last year, wasn't too bad. Dl was pretty light in the morning, then was decently crowded from noon to 7. Once the party started the crowds weren't too bad except around the Hub/MS for the fireworks and the parades.
My son and I camped out about an hour before the fireworks, worth it for a bench. Of course there were people camping out before 7 by the castle. We didn't do any character meets, not our thing, but lines looked loooong. We probably got in 2 lines for candy, knew we could load up on the way out (brought an extra backpack-hauled 15 pounds right at the exit).
Many rides were pretty short waits. We did BTMRR 5 times in a row in about 20 minutes, right at 7. As Doug said, HM was long wait most of the night, same with SM, ST. Ton of people left after fireworks, carrying out the little ones. We were spent at 11, I imagine those who stayed until closing had a pretty empty park.