What editing software do you use? I have been hesitant to buy something since I don't know much about it.
Final Cut Pro is what it says in the description on Vimeo.
I agree w/ getting a tripod - it'll reduce camera shake and make tracking a lot smoother.
One other idea is when you're framing jumps (like at around 1:02-1:10 ish), try to keep the a bit of the lead in/at least the bottom of the jump in frame, if you know how high they'll be going. As it is you had the middle of the jump at the bottom of the frame and a lot of empty space at the top that the rider didn't hit.