I just love the expression you caught here. What a seriously great capture. The color is really great, and the composition (previously mentioned about the tree not filling the frame) doesn't bother me at all, nor does the fact that the balance is off. The negative space on the left does it for me. I also really like the bokeh.

The only negatives (and I wouldn't even really call them negatives so much as could be "improved upons" or "keep in minds") is that, again, when you have the extra room in exposure, I'd have kicked down the ISO to 200 or move the aperture up a bit. 1/200 isn't crazy high shutter speed (and maybe he was moving fast and you needed it - if so, ignore!), but if you can afford loosing a bit, I personally feel DOF or noise levels are more important.

Overall, like I said, I love this one I think it's very successful.