Regarding what "sounds" hot, I think 100 makes more sense as the "super hot" number than 40. Although both numbers are arbitrary, 100 is less arbitrary. (Sorta. We just culturally define 100 to be an important number) Fahrenheit makes more sense if you think of it as "0 feels super cold, 100 feels super hot" although I'll admit it's a little strange that room temperature is 3/4s up the scale. That could be solves with a logarithmic scale, but that would probably be worse than either system.