I wouldn't call this a bad game, but it's hardly a particularly good example of its kind. Not being able to mute the sound effects, as annoying as they are, is definitely a minus. The automatic hints are more of a distraction than anything else - if you don't want people getting stuck, just add a hint button or the like, no need to make the screen start flashing without user input.
And then there are the pictures themselves. Once again, they're not BAD(quite the opposite, in fact), but... well, unless you add other elements(such as a story) or screw up, the quality of pictures is all people can judge the game by (since the gameplay is both rather simplistic as well as mastered by numerous existing games, and the entire focus of the game is looking at the said pictures) and therefore unlike with other kinds of games "good" is not good enough, the picture selection must be excellent. While this is highly subjective, I don't really think the pictures in this game manage to clear that(admittedly high) bar.
That about sums it up, I think. The gameplay needs a little polish, and the pictures lack that "wow"-factor that makes me really enjoy spot the difference - games.