i listened to this yesterday but ran out of time to reply.
as meerkat said, midi trombone is shockingly poor, so it didn't sound like it should've. Technology aside, it sounds great - there's not nearly as much music around for trombone as there should be so... more please
one thing i thought was great was giving the trombone some breathing space in its solos to do dynamics and phrasing, and be heard, by laying off the rest of the orchestra a bit. also, you're certainly using the bone's range

- god help the performer of that. and the bassoon solo about halfway through - great stuff, nice and playable, would sound good on a real bassoon, and having the soloist and orchestra interacting like that is great stuff. and you're not just sticking to one favourite section - w/wind, strings, brass, percussion, all get a look in with good parts.
possible critisisms... having trouble thinking up any actually! possibly develop your da da daa da da daa motif ('bone bars 10 - ) a bit more... hmm... maybe going around some distant keys (a la development section) and seeing what comes out of it... but seriously, this is good stuff. now, for someone to invent a computer that can make an instrument sound like it should...