There is tons of information about MNSSHP on the forums.
MNSSHP ticket holders have to get a bracelet. This lets CM's know you purchased a ticket. Without the bracelet, CMs will politely ask you to leave. You will not be allowed to ride any rides without a bracelet. This is due to the fact that the park is open right up to the time it closes for the party. It used to be that they herded you into one section of the park while they set up for the party. No longer.
Parade viewing does get crowded for at least the first parade. The second one is least crowded but much later. A lot of parents leave with their young children right after the fireworks. I tend to let mine sleep and rest all day, knowing we will be out till 11:00 at least.
Depending on the night you pick, it can be crowded. Especially the 31st and Friday/Saturday parties. Locals come in for the Friday/Saturday parties a lot.
While it is never really that crowded there are lines for the candy and some rides. Candy is included in the price of your MNSSHP ticket and they tend to load you up.
There are dance parties spread out throughout the park. Characters also dress up: Example: Minnie is a fairy princess, Pooh is a honey bee, etc. Cinderella's coach is decked out in lights. There is usually a long line to greet her there. Some places to eat are open, but not all. Special event merchandise is available like T-Shirts, photo frames, light up toys, etc. Photopass is available during the evening and last year they gave a 50% discount on photos from that evening.
In years past you have been allowed to enter the park at 4:00 with a MNSSHP ticket so you did not have to waste a regular ticket day to get in earlier. We always plan a dinner at Liberty Tree Tavern where for around 4:30. Some servers will paint their faces and the characters come out in their Halloween outfits.
It is totally worth the money to go. We have a blast.
