Just returned from a great trip! We attended the Halloween party on 10/14. All in all, we had a great time. It was pretty busy, lines for the treats moved qickly though. The lines to meet characters were long. We waited about an hour to meet Jack and Sally, but it was totally worth it. They were so much fun and were so much in character, we loved them.
My only complaint is how crazy it was during the transition from the park "closing" at 7, to the Halloween party. For a while, you had all the guests at the park leaving in a mass exodus, and tons of Halloween party attendees coming into the park. It was crazy, and so, SO crowded. Trying to walk into the park against the sea of people leaving the park, was stressful for us. Honestly even though they were checking wristbands through the night, I don't know how they would be able to tell who actually had paid to be there, and who was just still hanging out in the parks from earlier in the day. I think our wristbands were only checked twice, the entire time we were there. It was so crowded, that I think it would be pretty easy to just have been in the park earlier that day, and just sort of lose yourself in the crowd and get to stay at the party for free, essentially. I know they try to make this transition easier by letting party attendees enter the park a few hours early, but honestly, it seemed that the bulk of the party crowd came into the park around the same time we did, which was around 6:00. So in that regard, I feel like it was pretty disorganized. Between 6 and 7, when you had both regular daytime park guests, and party attendees, it was the busiest I have ever seen the park, in all the times I have gone (but I must admit, I haven't been there during New Year's lol!).
Other than that, we had a great time. We got a ton of candy and DD and DS had a blast, so in the end, that's all that matters!