Excellent stuff! There are many good things that can be said about this particular piece: the overal composition, the mixing, the arrangement, as well as the overal 'feel' of the song. Heck, I could even picture this being used in a film!
There are a few minor issues that could be improved upon, though:
1) The ending is a bit too sudden in my opinion. I was waiting for that final last note to come, but it didn't: it remained silent. It's a small thing, but an important one nonetheless.
2) Although the mixing in general is excellent, the vocals are somewhat hard to hear at times, especially during the busier parts of the song.
3) I get the idea that there is a little bit too much compression in some areas. Although it is an interesting effect on its own (and greatly subjective, too), I think it would've been better if the compression were more transparent.
Like I said, these are just small issues in an otherwise amazing song. All in all, a 4.5/5! Keep up the good work!