I don't think they would run hotter, as long as they were properly aligned,fit the pulleys, and were withing torque and RPM range.
I've heard of them before, but don't recall actually seeing them in standard V belt configuration. I don't understand how they could work on a standard sheave without the top hitting the outside of the sheave before seating down in the V. maybe they use special sheaves? About the only advantage I could see would be vibration resistance, or throwing on shock load.
I have seen them in metric sizes. Common on imported machine tools, called Polyflex. They are a polyurethane belt, oil resistant, smooth running, less vibration and flopping. Intended to give smooth, steady motion for precision machine work, getting a good finish with lathe work, etc. Very expensive!