Thanks everyone, I appreciate the comments.
For those who think the shot doesn't look level: try dragging your browser window partly off-screen so you can only see the right half of the image. Does it still look crooked? I can see how the slope of the ground on the left combined with the angle of branch can give the impression of being uneven. I guess the image looks fine to me because I know that the ground on the left sloped off and wasn't flat. This is one of those shots where I don't think there's any true horizontal or vertical indicators in the image; since I did level the camera when shooting I decided to just go with the as-shot angle. It may be off a fraction of a degree, but there's just no way to be sure.