Ok you're missing my point - the huge difference is in the ambient temperature - it is a lot easier to cool the coolant back down (after it has done its job) if the anbient temperature is cooler - in fact, heat transfer is a logarithmic process, so a 20-30 degree difference in ambient temp is huge. If the outside temp is 100 degrees, the water coming out of the radiator is probably still 130-140 degrees - which increases the chance of boiling after another trip through the engine.

And viscosity IS the issue - go here

http://www.overclockers.com/articles609/index02.asp

Here is a key excerpt:

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Antifreeze vs Methanol
What we're looking at here are two very comparable substances. The differences between them are often times negligible, with Methanol generally acting a little bit better then Antifreeze. Where the differences REALLY become evident is in the Viscosity. The Viscosity of Methanol is what really gives it a HUGE lead over Antifreeze from the word go; and the colder it gets, the more apparent that fact becomes.

Antifreeze is most definitely a great product for cars because they operate at 200+ degrees. Viscosity doesn't become much of an issue in that kind of heat because heat thins it out. Methanol would be terrible in a car because of its extremely low evaporation point. Alternately, it's also why Antifreeze is going to be terrible in your computer. Viscosity becomes a BIG issue in computer cooling, especially the colder you go.
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Yes - water is the most EFFICIENT coolant, but it is not as EFFECTIVE in automotive application because of the low boiling point. (Which is what I should have said in the first place)