Hey Andy
Well, they're works similar to Shimano SLR+ IMO (that kind of servo beeing in M900, M737, M095 levers etc), but are a bitmore problematic in adjust (brake arm is moving a little in wheel rotation direction, so pad position to rim is changing a bit) Also, servo mechanism must have springs inside so the levers maybe works a bit harder (but I didn't feel big differents to standard brakes - that depends also of set of springs' strenght)