There were a couple of gems on the OST...Both of Shingo Yasumoto's tracks "Hammerfall" and "Spiral Maze" (but especially "Hammerfall") and "Comes Off Run There" from Nakamura. But those are really the only tracks I listen to on it. It's sort of a dark industrial/techno sound with some occasional rock or orchestra thrown in. No way I could justify dropping $30 on it, but "Hammerfall" = <3. I can listen to that groove for hours.
I have to keep an eye out for Yasumoto though...Hopefully he'll get his own soundtrack one of these days.
Edit: @Xlord: Hey, Dynasty Warriors is a great series to draw inspiration from. Only flaw is the game probably isn't worth shelling out nearly $500 to play it (read: it's no killer app), when you can just snag DW 3, 4 or 5 on the cheap and get 30-40 hours or more from each. Other than Ace Combat, my favorite action game/series from this generation.