I can't say they are a bad gasket but I did manage to have one leak on me, by no fault of the gasket however. I had a wastegate hose melt. The head lifted. The gasket never blew but it did leak after this. Compression was going between cylinders and to 2 of the coolant jackets, but the gasket was still completely intact when I changed it.
Also two years ago detonation cracked the thin area between two cylinders on the embossed layers of another cometic I had. I have seen HKS do this as well but not on any of my cars. I cracked an HKS stopper gasket after driving near 30 hours in 1 weekend. The dowel pin expanded and the gasket cracked from the edge, through the dowel pin hole and to #6 on the embossed layer again. Seems to me you have to watch the embossed spring steel layers. Appears they get brittle after many heat cycles. My preference is the greddy gasket now. I think they are using a different alloy, or temper spring steel, or possibly both but I have no evidence of this.