Your edges are probably too hard; you'll want to exaggerate softness and details a bit in your high poly so that they transfer better into the low poly.
A minute or two in Maya. Starting from Transfer maps, set the envelope at the correct size, unparent it from the base model, clear history and export for xNormal.
Still just as awesome, I was having issues getting a few pistons to work together on a project recently. How much of the animation can be transfered to udk?
If you're polypainting on top of the retopo'd mesh, then zbrush will convert it to a texture well enough. If the polypaint is on a completely different mesh, I prefer using xnormal to transfer it.