This is linkbait. Joel's article makes it quite clear that he means Trello is different from existing FogCreek products. I don't see him suggest anywhere that

This is linkbait. Joel's article makes it quite clear that he means Trello is different from existing FogCreek products. I don't see him suggest anywhere that it is unique within the marketplace. First sentence of second paragraph: "Trello is new kind of development project for Fog Creek."