Aside from the incredible durability and longevity offered by cast iron, its density and weight are excellent at evenly distributing and maintaining heat. This helps you cook with very even heat (even if you stove has a hot spot or two), ensuring that your yolks don't get done before your whites, or that a portion of your pans' content burns while they rest remains underdone. This does not mean you can't burn stuff with cast iron, however-we're not talking magic wands here.
Plus, because of its weight, cast iron will not warp under high heat, making it a great option for searing foods that need a crisp outside and soft inside.
Beyond the stove-top benefits, there is lots conflicting information out there about whether nonstick pans can harm you with chemical offgassing. Research has shown that heating nonstick pans made with "Teflon" (which contain PFOA) up to above 500°F-admittedly, hotter than you'd normally go-releases PFOA and other chemicals into the air, where you can breathe and be sickened by them. Consumer Reports debunked this, asserting that the risk of nonstick-pan use is very low, and getting lower. Still, while the jury remains out, we'd prefer not to have to gamble our health on it.
Difficulty level: Moderate