Listen to this piece kind of makes me miss writing out full pieces. I've spent a little too long writing loops for video games. xD I love this song and it's what compelled me to favorite you as an artist. Well, about time I took some time out to review it.
In any case... the critique.
Structure-wise, the song is relatively simple and short. However I do enjoy how it goes through thematic development in the short span that it has. The break at 0:42 is sort of abrupt and leaves the listener hanging after such an epic motif. While its discomforting (to me at least xD), it works effectively. The piano part afterwards works well as a break from the epic theme. I personally love an excellent piano part. While the piano part does accomplish its job, it could certainly use some development when it repeats itself as the other instruments return. Also, at around 1:00, some soft timpani rolls may also help with the atmosphere.
And now that I mention it, I have to critique you on it. Your percussion is something I think could be changed. The song sounds excellent as is, however when it comes to an "epic" or "heroic" piece, percussion has been an essential element in most compositions. Even the smallest amount (such as quiet timpani rolls) help. DavidOrr, MaestroRage, Hans Zimmer, and other famous artists for "epic" music make prolific use of percussive instruments. And if you listen to each artist's discography, it is also the use of these percussive instruments that defines their music from the others. Zimmer loves the tambourine, and uses it religiously (and to a fault in my opinion). I suppose you should try having a section where the timpani can stand out for a bit (take the limelight). Also adding a more treble based percussive instrument can help with the pace of the music (e.g. tambourines in Zimmer's music and snares in Orr's music).
Now outside of that, I think your composition of the song is excellent. The next part of critique is one where many (including myself) need work on. The sound. Focusing on composition comes a long way in making a song sound excellent, however knowing how to record (which most of us don't need to worry about) and mix the many sounds of the instruments can make a song sound much better. While orchestral pieces (and more classical orchestral pieces) usually mix themselves just by composition, adding EQ to help place the frequencies and using compression to bring out certain aspects help create that "epic" sound. Your song is "epic" already, however I think if you mixed it better it can stand out more.
Nonetheless, I believe that composition is more important than mixing and that you have nailed well.
Great work on this song! I already have it on my Ipod. :P
I look forward to hearing more from you. ^__^