Ahhhh!!! Warm house in the chilly autumn :-)
Not only are the new Energy Star windows good at keeping the cold out, they're also good at containing the heat.
My Dad is visiting and staying in our basement suite, so I have the electric baseboard heater turned up to 20C (68F) for his comfort. I am noticing that the entire house is warmer, whereas for his visits prior to the installation of the new windows, the heat on in the basement would not have made a difference upstairs.
This to me reflects the benefit of the fact that the heat is no longer escaping through drafty basement windows...