This was pretty cool given your limits for the project. If you used a soundfont or VST that adjusts timbre at different velocities, then I think it would sound more natural; your softer dynamics would become less harsh. Overall an enjoyable composition!
You are the exception...
This kind of experimental/classically complicated songs is missing nowadays. In my mind, the song doesn't really give any images... Only the slight sight of a vortex filled to the brim with darkness and imagination. I can't believe that people are still able to write like this in 2010. Either you have very good teachers, either you have a gift. I bet on the second option. Keep it up, seriously! Those songs stand out in your library of tunes!
Please contact me if you would like to use this in a project. We can discuss the details.