On another point a high frequency yaw damper (it must react quickly to be of value) makes a huge difference in the handling qualities of most aircraft in turbulence, but the autopilot servo used for a yaw damper, that I test flew in a Lancair was not capable of responding fast enough to make a significant difference. A yaw damper will not reduce the requirement for right rudder on takeoff, climb or descent. What it really reduces the tendency is the tendency to have yaw excursions and dutch rolls.

 
   I flew a test at Edwards where a high frequency yaw damper was installed in a Twin Comanche and the difference was very noticeable. So it does work in GA aircraft.