I should probably play through it. I bought it on sale during a steam sale a couple years ago, but have yet to load it up...About how long is it? 3-4 hours?
You could probably blast through it in 3-4 hours, though if you explore around for all the sidequests to get all the costumes/skills, it'll end up a little higher than that. Also the PC version includes the DLC for free, so you can also play Grubbins on Ice which is winter-themed if I remember correctly. It's maybe about a quarter as long as the original game, so let's say that DLC is something like 60-120 minutes?
I guess I'm the only person who vehemently disliked Costume Quest and would never think about touching it again? For a game that is only 4 hours long, I was wishing death upon myself after the first 60 minutes.
I felt that a lot when I got 'stuck' because I didn't go trick or treating at all the houses or I missed some small thing but I suppose I feel that way often with those kind of adventure games :/