The first three chords made me think that your piece would turn into a remix of the Hyrule Temple Theme from Smash Bros. :p
I love this piece. Catchy melody, rhythmically driving, full of good transitions, structurally sensible, dynamic, and harmonically creative. At 1:39, I like that ascending chromatic bass movement from bVII, V6 to i. The chromatically descending bass a little after 2 minutes is also nice. I LOVE the bVIMaj7 chord at 2:46. Nice way to change things up. I also really like how you go from iidim to v at 2:48. I wish more people would use those tense diminished chords. And bonus points for using v from natural minor instead of V with the leading tone. I love the mellow sound of v...
The instrumentation is very effective. Starting at 2:51, I love the decorative piano lines. I also really like the high pitched bell sounding instrument that plays on the down beats starting around 2:21. Oh yeah, and I knew this piece would be awesome when the bass guitar rolled in at the beginning. >:D
However, I didn't care for how muffled the vocals sounded throughout. Everything else was so clear, but the vocals sounded underwater for most of it. Maybe that was an intentional choice, but it just didn't sit well with me. The panning at 3:11 was very interesting. I'm still not sure whether I like it or not. The vocal part at 3:51...I get what you are trying to do, but it seems to me like it was not as effective as it could have been. I believe you come in there singing on the bII scale degree. There is so much tension there that it feels like the climax of the song. That note usually serves as a sort of downward pointing leading tone to tonic and I want to hear it so much! But the line then meanders around feels like it falls flat. I think it'd work better if you held that bII, dropped out, let the guitar do its thing, and then hit tonic hard when you come back in. That part just put a bad taste in my mouth. My little brother who was casually hanging out in my room inattentively gave me a sudden, confused look at that part.
With the exception of that one part, I really, really dig this. I hope that you eventually redo this piece and clean it up a little, because it is awesome and could stand to be even better.
Keep 'em coming!