It's still building up an index just now, so it can't find things too easily yet. Hopefully though, once it's more fully developed, it'll be something that will be a big help to artists wanting to make sure they haven't been ripped off.
EDIT: Since someone asked, I ran a test using an image I had edited. I used this image, since I figured a celebrity photo was more likely to have been indexed already than most. Search engine found a bunch of matches when I blocked out the eyes and mouth with a black strip, but blocking out the face made it fail (about 1/3 of the image). Still, it seems to work pretty well for smaller edits, and I would guess that for most people's purposes it'll do the job fine. Just as long as they actually get around to indexing enough images :p