Hi BSA,
I have a bad experience with the old kickplates, I tried them twice but I removed them twice because of the bad shifting: I regularly found myself "pedalling in the air " when the traffic light was becoming green. It appeared very difficult to balance the preload between the 2 kickplates.
A big advantage of the kickplates is that you can’t loose the shift buttons… 
Did Schlumpf reduce the stiffness of the kick plates or are the the magnets so strong that they can always keep the kickplates in contact with the crank levers?