They key with cast iron is using enough fat, which is generally more than you'd use with other cookware. High heat just burns the fat and/or the food, ruining your meal and making cleanup more difficult.

What cast iron is really good at in terms of heat is retaining it. There's enough mass that you have to preheat the pan for longer, but once it's hot, it stays at a pretty stable temperature when you add your ingredients. It doesn't get hot spots as severly, either, especially if preheated for a good long time at a relatively low heat.