I have to turn it off. Kinda makes the game less scary than it already is. Other than that, amazing game.
Yeah, I turned it waaay down--almost muted. I found when I was most enjoying the game was when it was just the sound of my footsteps echoing down corridors, ears straining to hear any nearby enemies and where they might be waiting. Then I'd cross over into an area where the music would kick in and just...ugh. Atmosphere ruined.
I got annoyed with the music during the medical/crew quarters section, and finally turned it down to almost nothing in Engineering (where IMHO it's even more obnoxious). That kind of music is better for something like Doom where you're fearlessly mowing down enemy after enemy, not the careful "picking your battles" type of combat I've been doing in SS2. Nor is it well suited to listening to while you're trying to listen to the audio logs...it drowned out the dialogue more than once for me before I finally turned it down.
I was surprised to see so many people on here praising the game's music...I'm sure it's okay to listen to on its own, but when heard in-game it pretty much ruins the game's atmosphere for me.