Not bad, but...
I'm a complete DDR freak, and while this may be one of your harder submissions I AA'd it on the first try, so I think if you're going to label it as being really hard, you could add long freezes and 16th-note drills, or you could make us try to hit more than two symbols at once (for the Oni mode players). It is still challenging, however, and it is loads of fun. But I think it would be really cool if you could get a larger selection of music into one game. It would also be more engaging if you could get some sort of background. Still, a good submission.