We LOVE the Halloween Party! In fact we'll be in WDW when their first parties start this year and we HAVE to go (even though it'll be mid September and no where near Halloween mode for our brains). It's definitely worth it. If you are going to the parks as well as the party, I'd use the party time to concentrate on the party festivities instead of rides, when else can you dance with your favorite characters or meet rarer characters and classic characters in their Halloween costumes. The fireworks are amazing. I haven't seen the parade they do in
Disneyland (last party we went to was at DCA).