I noticed that you said that you use sibelius.
I would recommend that you export from sibelius as a midi file then import the composition into a program like FL Studio or something better if you have the money.
Other than that, I really like this composition. That said, I'm still giving you one hell of a review.
The whole first half was great, I have to say. After that, when the bps changes and it goes to 6|8 time, it seems to go to the E minor scale (not the chord, I hope you know what I mean) in certain places, and not too smoothly either. More like suddenly and unwelcomely. That seems to be the only problem that I can find in this song other than the fact that it's a sibelius piano.
Actually a few things are now coming to mind. Not telling you to redo your whole song, just throwing a few suggestions:
The first half seems to have much more energy than the second half. Maybe you might want to think of switching those two halves so that the song builds up as opposed to slows down.
Maybe you should have ended on a powerchord instead of a minor chord. That way, the A note can still be the most significant note there, contributing to the sense of finish, if you know what I mean.
That sums up my review. Really nice song, I wish I could actually play this on the piano.