For the type of music it is, it's pretty good. I'm not real big on the ambient orchestral sound, but it will probably not suffer the fate of everyone turning off the music because they don't want to listen to it. (Wanting to listen to something else instead, that's another matter.) I haven't checked the actual staff involved, but it's probably the same composer as Diablo 2, if that gives any indication.
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Only the exceptions can be exceptional.