Yes it will work. Just instal the controller and in Halo activate it from "gamepads" something... I don't remember good, but it was easy. It does not support aim assist (which is one goddamn good thing) and when I used the controller, I keeped moving and/or even when I wasn't touching the analog sticks. Just because it's not accurate as mouse.
I think the really screwed up with Halo 2 pc version's mouse controls because theres no way to turn the acceleration off. So I understand you well if you've played Halo 2 Vista before and now you want to play Halo PC/CE with controller.