Not Bad
I tried it on a perfect American Sycamore leaf collected from a specimen just a bit outside the normal range. The app doesnt like any image unless the leaf is on a pure white background. On a piece of unlined white paper I took four images in succession. Their server did an okay job and returned the right answer at positions 2,3,4, and 2. (First was Amur Maple.) But the returned reference images made it really clear that my leaf was a Sycamore.
Wald76 about
Leafsnap