Built-in heater apparently will give me a sanitizing option to my washing, which is great for pet bedding.
We thought this was a great idea and it was one of the reasons we were glad to upgrade to the Duet (the old Kenmore/Frigidaire did not have a sanitize cycle). But the sanitize cycle ruined our towels, shrunk the cover on the dog's bed, and made our diapers look old and worn in one shot.

We just use "heavy duty" now. The sanitize cycle is REALLY hot.