Dave, light fixed wing use a servo-flap as elevator trimmers. The fact that airspeed is so stable in gusty conditions says that response is fast. If there was a delay, for helo applications, some swashplate lead could be added. If response time was a concern the servos can be designed in as part of main controls for flight load relief.
To be honest it suprises me it is not more common, since it is simple light and effective...
