I've sworn by these tires since I started using them. Everytime I try something else, I regret it.
I have used the S12XC on my KTM450 and YZ125, front and back. I'm 160lbs (without gear), ride A Open, and use 12psi front, 10psi rear. I've found at my weight and speed, those pressures provide excellent compromise between grip and flat protection. Only 1 rear flat in 3 years of racing hare scrambles/enduros. (50-something races). No front flats at all.
These tires HOLD UP!! Last weekend, at Boogieville hare scramble in Uniontown, AR we saw some of the rockiest terrain out there. Going in with a new set of S12XC's, I had comments on how my tires looked brand new AFTER the 2 hour race! And they almost did :) Front - NO Chunking. Rear, could just barely tell it was used.