I've heard so many different things about the safety of non-stick pans like never heat it while empty, never heat it higher than medium, and such so the pan does not release toxic fumes (PFOA - a carcinogen). So what about the non-stick grill? It's supposed to be used for searing meats at very high heat. I am tempted by the Calphalon Unison Non-stick grill from Williams Sonoma. Or should I just stick with the cast-iron grill?