PSB
Nice job, I guess if there's one thing you can improve it's to get better vsts. One thing the instruments may sound stronger if you use multiple layers in the piano roll for each instrument. (Except maybe the flute) See:
http://i45.tinypic.com/2cyfds8.jpg
Not to nit-pick but you could make the kick a tiny bit louder and hi-hats softer.
But I give you credit the beat's great already. Fuder fuder fuder!