I put these tires on my Fiesta ST to replace worn and old Pirelli P Zero Nero on the back, and viking pro tech newgen on the front. I bought the car with these mismatched tires.
The Kumhos offer excellent dry and wet grip, okay comfort for a 40 sidewall. Still too jiggly for my liking, but that is not the tire's fault. Progressiveness at the limit dry and wet is amazing, very easy to correct, if you get it to break loose at all. You really have to throw the car into a sharp corner to get the back to come around. When you do, you feel the sidewall flex quite a bit, and then the tire progressively lets go. On my Fiesta ST, the car will also lift the inside rear wheel quite easily like this.
At Autoslalom (AutoX), the tire shows its soft carcass even more. I experienced a lot of low speed understeer, and the tire showed clear marks of rolling onto the sidewall multiple centimeters. The outer tread blocks showed diagonal wear on the outer edges of the blocks.
While the tire is great for grip and progressiveness, and noise isn't too intrusive, I am disappointed in the soft sidewall on this 40 series tire. Steering feel isn't great due to this either. To me this tire feels like a very good daily driver with buckets of grip, but without a real sporty edge at the limit.

