My wife and I went last year on october 25th. The park decor is just awesome with everything lit up purple, green and orange. The grim grinning ghosts derge playing on the main street sound system was very cool too. Loved the villians parade. Some of the villians got booed by the crowd and they went by and the CM's totall ate it up... they loved it!!
Piece of advice if you are staying in the resorts... leave early. You'll be on a bus, boat, monorail with a LOT of strollers. So they fill up pretty quickly. We left got to the bus stop at Boardwalk Inn 30 minutes before the opening time and had to wait for the 3rd MK bus.
But other than that learning experience, and the huge downpour 30 minutes before closing, it was an awesome time.