For some reason it took me a while to get that the stories were draggable. I understand you are going for a clean look, but maybe a handle would also communicate it it draggable?
Also, push the mobile aspect. The site makes sense on the ipad or a smart phone. Unfortunately, I cannot open the story data overlay from the ipad.
Also, try to have the overlays somehow originate (using animation) from the store or backlog or finished button.
Also, you might want to try a dotted border to separate the phases (not sure about the terminology).