Being a Chinook Pilot....our force trim was always "ON"....and when one hit the Trim Release the Cyclic reverted to a "Zero Friction" state and became a limp ....errr.....errrr.....noodle. Instantly one could feel the difference in the movement of the aircraft even if only very slight. The Thrust Lever (Collective Lever for you unenlightened Skid Kids) had a separate switch for the Thrust Brake....very strong force trim....very strong! As our good friend Dixson notes.....widely divergent oscillations can occur...and oft times presented us with a ride similar to that of a Bull Ride on steroids. The only way to stop the Thrust Lever from moving was to re-apply the Thrust Brake and apply a blocking of the lever using your knee.
The Bell SCAS system which started on the Cobra used a similar concept as did Sperry....a minimum friction setting for the cyclic as I recall....as on the later Bell 212 SCAS equipped aircraft.
If an aircraft has an attitude hold SAS system such as the 212/412/76/and a host of others....why not set the attitude you want...release the Force Trim Switch and let the aircraft hold the selected attitude. Did we not all learn to fly "attitudes" from our first lesson in a helicopter? Even on the HUEY, with no SAS system...I used the Force Trim system all the time. Still got the calloused Thumb all these years after retiring.
Smooth is good....burns less fuel....takes less muscle....and certainly less thinking....all good things.