Mmm,interesting. Wouldn't CR-props get rid of the critical engine on a twin, for one thing? (downgoing blade produces more thrust than upgoing, hence on a twin with two 'regular' props one engines' thrustline is offset closer to the centre than the other, etc, etc) Also, surely the airflow behind a prop, whilst definately tremendously accelerated relative to the still air in the surroundings and also possessing a vortex-like swirl, is still simply a mass of air meeting the prop at a certain velocity, and not a sea of crazy turbulence? Therefore, all that is necessary is to have the blades at the appropriate pitch angle and you're ok?
Must be a complete and utter bitch to build and maintain, though, for just a little bit more power.