I know you can make splendid cornbread in a cast-iron pan, and Southerners say it's the best thing going for fried chicken. I've never used one that way, though. I've made more platesful of crusty O'Brien potatoes than the Chasen's chefs do in a month, but never pan-fried lake trout in cast iron, nor baked a clafoutis.
A cast-iron pan can do anything you'd expect from a $280 tinned copper sauteuse , but I like cast-iron because it's the world's second-best grill.
If you heat cast-iron to the point where bluish haze veils the bottom and a bead of water dripped upon it explodes into steam, you can sear a piece of salmon in a couple of minutes, grill a scallop in less than one. Leaves of radicchio blacken and turn sweet in practically no time; ultra-hot habanero chiles blister and char and develop a fruitiness they seem to get in no other way. (Open your doors and windows wide.)
If you carefully lay down a rib-eye steak onto hot cast iron, first perhaps rubbing the meat with olive oil and salt, it develops the sort of irresistible crustiness that is impossible to achieve in the average gas broiler, even when you leave the inside blood rare, and an average supermarket steak stays juicy as the $32 expense-account jobbies they serve at those places in Beverly Hills. Cast iron is cheap: The extravagantly well-seasoned pans you can pick up at swap meets and Palmdale junk stores may be the best two bucks you'll ever spend on your kitchen.