Cool!
I like it a lot. As I listened, I totally thought this would go well if 'Mouse Guard' were an animation or something-- sounds like a good "Mice doing battle" theme. My favorite was at 2:18 and how it builds up.
The things I think drag this peice a bit is the piano and the snare drums-- it sounds way too synthetic. That and I feel there's 1 or 2 too many silent parts in the song.
So I enjoyed it very much. Hope this review helped out. Either way, great job!