On the DH8-400, all three trims find much use in case of a power change. Rudder trim will obviously be required due to the tremendous P-factor; Elevator trim is needed because of the prop wash induced changes in lift, requiring a readjustment in pitch. And while the banking moment caused by torque changes is small, it is definitely noticeable and requires a bit of aileron trim adjustment as well. On some of our -400s, reducing power for descent might even cause a MISTRIM - TRIM LEFT WING DOWN message when the autopilot is engaged - with the aircraft trimmed for cruise power, the always present banking moment to the left is countered, but when one reduces the power, the engine-induced banking moment is reduced as well. This seems to result in a load on the autopilot servos sufficient to cause the above mentioned message on a few planes in the fleet.