I'll give a quick report on our parties-- we went on 10/13 and 10/15. Neither were sold out. Our goals were to get photos around the park and with characters in our costumes, plus watch the parade, fireworks, and Hocus Pocus stage show. No trick-or-treating or any rides/attractions. My wife and I dressed up as Alice and Mad Hatter on 10/13 and Tinker Bell and Captain Hook on 10/15.
Both days went about the same. We arrived at the gates around 3:30 and they started letting partygoers in around 3:40 or so. We had already set up character meet FP+ for between 4:00-7:00 pm so we spent the first couple of hours using those plus doing some other M&Gs that didn't have long lines and taking PhotoPass photos on Main Street and in front of the castle. We grabbed a quick dinner at Cosmic Ray's about 6:00 pm then got in line for our first characters. We used Kenny the Pirate's Character Locator to plan our schedule, and we had already decided to skip the Dwarves and Jack and Sally. We did character meets until about 9:30, then found a spot near Crystal Palace to watch the fireworks. After the fireworks we did a couple more character meets in Adventureland, then found a spot for the second parade in Frontierland. After the parade we made our way up to the Castle and watched the Hocus Pocus show at midnight and took several more PhotoPass photos, then left the park.
On the first night we met the following characters between 4:00 pm and midnight--
Tinker Bell
Tiana and Naveen
Cinderella
Rapunzel
Anna & Elsa
Minnie
Daisy
Donald
Goofy
Alice and the Mad Hatter
Queen of Hearts
Pooh, Eeyore, Piglet, and Tigger
Witch from Snow White
Tarzan and Jane
Aladdin and Abu
On the second night we met the same characters minus Aladdin and Abu, but plus Cruella and Jafar. Came out to a total of 24 characters met each day.
All in all we found things manageable and had a great time at both of the parties!
Here are a few pictures: