It was one of our best nights of our entire vacation last year!
The "Boo to You" parade is just awesome, (I think one of the best parades at Disney) and like others have said you can't get the "Boo to You" song out of your head afterwards.
MNSSHP offers a lot...our advice, do the face painting and pictures with Cinderella's Coach early, as lines can be long later in the evening. Take advantage of the special events: Character Dance Parties, Villians Mix & Mingle (in front of the castle), picture-taking/seeing rare characters that you normally don't see often at Disney, trick or treating, the parade, fireworks, etc.
Lastly, enjoy some rides if you have time. Towards the end of the night, especially after the second parade, the crowds thin out and you rarely have to wait in line for the rides. We usually try to do the rides last, because, in our opinion, you can ride them any other day at MK (and usually without a wait if you take advantage of EMH), but you're really paying for the special events at the party...so get your money's worth!
Make sure to eat before you go (so you don't waste party time dining, plus you can always get a snack or munch on your candy while waiting for the parade). Also, arrive right at 4pm (your tickets might say 7pm, but they'll start letting you in at 4pm). One more thing, use the PhotoPass Photographers in order to get a really good family photo at night. Most of my pictures, that I took once it got dark, didn't come out near as well as the one's the Disney Photographers took (and I'm a Scrapbooker with a good camera). You'll want to capture all the changing colors of the castle and the "spooky" light designs up and down Main Street and sprinkled all over the park.
You'll have a great time...don't forget to dress up!
We're going September 16th and can't wait!
