Could be great to have raytraced & geometry based motion blur as in mentalray, vray, mantra or renderman interface compliant renderers.
I don't know if motion blurred shadows can be achieved with raytracing, as in mantra it is only available with shadow maps.
Actually I think only Aqsis, Pixie, Sunflow (camera blur, not sure for geometry), and some of the free unbiased/hybrid renderers which have blender exporters, have the ability to render geometry/camera based motion blur.
Blender vector blur node works in some cases, but does not work properly with shadows, and thru reflect/refract objects.
Yaf already has DOF, but these two features will push yafaray to be a true photorealistic and a great animation renderer.