I wanted in Endefekt only the reason for the 4 star rating name that applies to 95% of all controllers in the shops and I've caught a back here.
The so-called "Slow Turn" occurs because of a Konstriuktionfehler of the controller, which has not been removed to this day.
It occurs because the holes around the 3D sticks are too tight and the Herab- and Look Up is far more slowly than the left and right look.
Here helps only a Modifiktion which will void the warranty by opening the controller and increases the holes.
In my 5 year old controller I've done this successfully already and wish that this would be by default so.
Still, I highly recommend him!