If you have not gone, then you should go. Definitely worth going to. As for crowds, it seems every year they sell more tickets, so it's not really an exclusive party anymore. With some planning though you can have a great time.
Couple of tips:
1. Don't plan on going into the parks that morning. Wait until 4 pm when they let you into the party. I know the Party runs from 7-12, but they do let you in at 4. That way, you don't burn a day of tickets, plus everyone in the family will be charged up and ready for a fun night.
2. If you plan to eat, make a reservation at like 4:30 so you can get it out of the way before the party starts. Many rides are walk-on between 4-7 because day guests are exiting the park.
3. Talk to your kids and ask them what's important to them, shows, trick or treating, or rides. Your game plan will depend on how they answer that. Keep in mind, if you get there at 4 you can get many rides out of the way, which will leave you more time for the special Halloween stuff.