Oh, I'm not claiming to live in the most extreme climate. However, I come from Northern Minnesota and live in Central Minnesota. I have had my share of extreme sub-zero temps. Most of what I'm hearing here is anectodal. And my conclusions are based on anectodal evidence as well.

A block heater changes the whole equation. I'm not sure if you mean a car should have no problem starting without a block heater. If so, I'm not sure what you're doing to get to that level. Maybe putting kerosene in the oil? :)

My grandpa used to put a coffee can filled with flaming heating oil under the pan of his International Harvester pickup truck. Worked perfectly.

I have one simple argument: when the weather is far below zero and your car has been sitting out long enough to be the same temperature as the ambient temperature, you need all the help you can get starting it. Having the right oil weight helps. Having fewer things for your engine to turn helps (why the old 160s and such fire right up). And I think the preheater can help by making the engine that much hotter that much faster, and yes even while the engine trembles on those first turns.

-JSBB