I wondered about that, too---how fragile will this be in the face of minor GUI changes? (A fuzzy-match parameter would be a nice addition to the API.) One encouraging sign is that the screenshots are stored as .pngs in the file system. If an app update does nothing but change button graphics or text, the script could presumably pull new graphics from the same place.

That just leaves the other 90% of GUI changes that involve moving a setting to another screen, or changing the way an entire interaction works. ;-)

All the stuff you said about GUI automation being klunky is true. Still, this thing could come in handy as a kind of "GUI batch file," or perhaps as a tool to help produce screencasts.