Sounds like another +1 for the prius in cold climates. I have a vacant service road near where I live, so once I idle out of my community after having my block heater plugged in I have luke warm heat as my water is 132 degrees. I go for a 4700 rpm romp to 60 on this service road and after several seconds I can feel hot heat vs room temperature air come rushing out of the heater.
It seems once you get the water to 180 it holds its temperature better, but I think humidity pays more of a role in how auto stop behaves than anything else in the vehicle.