Yes, it is mostly a bunch of trick or treating. Though there are a LOT of characters out and about, so it's a great opportunity to see them if you're into that. Otherwise it's mainly a chance to ride the rides when the lines are fairly short, though we had a 30-minute wait for Tower of Terror last year. There's no special fireworks show like there is at the WDW parties. Also not much of a parade, though it was better last year, so I'm hoping they will add more to it this year.
I think it's fun - a lot of the CMs are in costume and everyone seems to be having a good time. The Halloween decorations are cool - they project spider webs on the sides of buildings and even on Grizzly Peak and Orange Stinger. There was a jack-o-lantern pumpkin projected on the loop in California Screamin' the first two years, but not last year because of the construction of Toy Story Mania...but I hope that will be back this year.