In my internet wanderings I thought there was speculation that INFI was a modified "A" steel (A2?) with the addition of nitrogen and possibly fairy dust. While the steel is proprietary, it's the heat treat process that really gets it into a good knife. I've had super steel blades chip and break. I've had supposedly fabulous carbon steels warp and chip without hard use. Then there's S7--normally, it's designed to not really take an edge, but was designed for high-shock applications like jackhammer bits. Yet, Dan has figured out a good protocol to make his SR77 an incredible blade. If the heat treat sucks, it doesn't matter what the steel is, the blade will suck. If the heat treat is good enough (and appropriate to the steel in question), you can (within reason) turn just about ANY steel into a good blade.

The best is when you get a good steel AND a kick-butt heat treat. That makes for a FANTASTCI knife. That's what Busse does. Their regular stable of steels are not powder metalurgy. But they are good steels (for most applications carbon steels tend to be better than stainless for quality blades--possibly discounting the new super steels) AND they've figured out arguably some of the best protocols for treating them.