The Denon DN-MC6000 is a dedicated Traktor controller and digital mixer. Cased in solid steel it has excellent build quality and can be used to control other DVS systems via midi. The DN-MC6000 comes bundled with Traktor LE and works with both Mac and PC systems. If there is a direct competitor out there that will give the Native Instrumenst S4 Kontrol a run for their money it should be this DN-MC6000 controller.
Denon DJ just released this demo video showing us more of the workings of the DN-MC6000.