If you are "into" Halloween, then yes, yes, yes it is totally worth it! If you are not into Halloween, well, you might still enjoy the short line rides and generally improved fireworks. The parties can be crowded, but most of the crowds are there to witness the party-exclusive stuff, so it centers around the hub and the unique party-only characters. If you want rides, lines are short. If you wait and watch the second parade it is much easier to get a spot as well. Generally it is a very enjoyable and different time in MK.