I tried it on this image of a gravestone [1], saved the low res version from the google image search results page, and it's obvious which parts it's recognized and which parts it hasn't. It did great on the flowers, but made the gravestone and the grass worse.
It's impressive, but it adds details that were never there in the first place. In the demo on the site with the colorful bird, the enhanced image is a different, although very similar bird.