Very cool. I like your use of rhythm (passing it from section to section is very effective), and the contrasts between different parts of the piece seem to work nicely.
My only complaint is the ending; it comes rather unexpectedly and doesn't really seem to provide the energy that the rest of the piece has.
You might spice up your rhythms even more, maybe experimenting with complex meters (I've found that a bar of 3/8 or 5/8 every so often can really liven up a fast piece if it's used the right way). The music of David Dzubay (pronovamusic.com) is a good example of this. Although his music doesn't really use conventional forms or tonality (which is why it isn't my favorite), his orchestration is very cool and his rhythmic intensity is insane. Specifically, look for a piece called "Ra!". His "Shadowdance" is also good (there is a section where he has 6/8 time and 7/8 time happening together with the downbeats lining up) for studying rhythm. Stravinsky's "Rite of Spring" is fantastic, as well (it pretty much rewrote the book on rhythm and meter).
Sorry for the long post! Guess I got a little excited...
