My problem with the OST thus far is the apparent lack of a distinct, iconic theme. Never mind the total absence of Halo's iconic monk chant.
I know they wanted to go something unique and their own, but it might just be a case of tossing the baby with the bath water.
You don't simply throw away a decade's worth of audio identity just for the sake of it.
As good as the music is, not a single track makes me think of Halo.
I grew worried about the soundtrack when I read an interview with Davidge where he was asked whether there was a central theme to the score, and he said no, but MS might pick one to use as the main theme. I felt that setting the Halo theme aside was a mistake, but it's odd to create the first score for a new trilogy and there's not a central theme to mark the new game, or series, with. I thought providing that sense of identity would be important, given the main theme was gone.
Not judging the score one way or the other, it's just a really strange set of decisions.