Really well done.
Very minor subjective comments:
1. I'd try and round out the piano in the beginning (probably just with eq around 1-2.5K or so, but you might be able to find something else - tube ****, tape saturation, or some other effect?). It seems just a hair brighter than the voc and is therefore competitive.
2. This may or may not be an improvement, but I'd experiment with just a little bit of some kind of ambience program or dual hard-panned delays about 15 and 40ms on the voc. That may not sound good, or it could integrate it a little better.
3. Same with the piano in the beginning maybe; I'd also pan its melody notes away from the voc a little. And the bass end of the piano sounds like a different instrument, which you may or may not want.
These are very subtle points, though - great mix. It's not easy to build like that while keeping the level even they way you did. I'm just lending you my fresh Roman ears, certainly not saying I could do better for one minute.
Oh, and it's too late for this, but there's a little too much D major for me. I probably would have modulated by the third verse.