The whistle in the percussion is really out of place.
I like the background strings in :40, they fit in well. As for the piano at 1:00, I'd suggest a less electronic sounding one so it fits in with the theme better. The guitar fits perfectly though, although maybe a few harmonies would sound nice with it.
The french horn (I think that's what it is anyways) has some slower sections that seem to draw the song out a bit.
I like the reverse cymbal at 3:06, but it'd fit better if it wasn't at the end, and it led into some nice harmonies and percussive beats.
Overall, nice piece, but it has some flaws (namely the whistle... which in my opinion doesn't seem to work as percussion unless you're composing for kids' music; it doesn't suit the genre or tone of this piece)