Crisp shifting on XX1 cassette with approx 3000miles on it, significantly better then SRAM'S PC-XX1 chains.
Nothing bad to say about these chains.
I alternate between three chains and swap after every ride, using KMC's included quick links. Doing this extends drivetrain life, and I swap out chains by the time they hit 0.5% stretch. Bike is ridden in all conditions. Using white lightning clean ride wax for lube.