I'm a little confused. Wasn't this posted a few days back? More to the point, though, I'm a little unsure as to where the DOF effect is supposed to be. Are the background trees supposed to be out of the DOF? If so, they are too dark to tell. I think this is a either a bad scene to try DOF on, or a bad angle, because so many of the major elements are the same distance away from the camera.
Still, it's not a bad scene, though. Although, I think your lighting could use some more sampling.