Great composition, but I'm going to nitpick a bit at your mastering. I felt that the strings came in a bit heavy after the intro, around 0:22. I would have toned them back a bit more, just to make the piano's entrance a bit more obvious. Also, I think you should keep the strings soft while that early piano solo's going on until about 1:30. Once you come to the reprise of that section around 2:00, that's when I'd let the strings come in harder. That way, when you have the strings carrying the melody at 3:00, they'll feel more built up. As it was, they didn't quite resonate as I felt they could have if they'd been building up.
The next section (starting at 3:30), with the piano carrying the melody should vary a bit more in volume, maybe start it even softer than you do now. I'd start building towards the crescendo at 4:08, with those 3 chords building up to the slide at 4:28.
I loved the way you reduced the volume after that. That's where I'd like to see the dimminuendo at in other places. However, I think the strings come in a bit too strongly at that point (5:02). Build them up gradually, because as you have it now they over power the piano as soon as they come in. I also suggest that you reduce the compression and the "heat" on the piano during all its crescendos. It's very strange to have it ringing on all the louder notes; pianos don't really do that unless the pedal's down, and basically you've got it down throughout the whole piece, particularly around 5:45.
THanks for taking the time to compose this one. It's a really great arrangement and it's not overly complicated.