I've only used it on cooked meat, and it's developed a nice layered patina. I have never noticed any discoloration on the food, or staining on the blade.
I'm still using the edge Pierre put on it, as it has no trouble dismantling whatever roasts I throw in its path. This past weekend it was a roasted pork shoulder. The slices were pretty effortless. It's tackled some rib roasts, pork shoulders, pork loins and a turkey. Some roasts had a nice crust, and others presented only soft surfaces to the edge.
I'll be snapping a few pics of Del passaround knife tonight/ tomorrow, so I'll shoot a couple of the suji.