I thought I had no use for heated grips in Southern Nevada either, until I found myself setting at lights with my fingers wrapped around the rear head trying to thaw my fingertips...
I absolutely love my heated grips! Initially, I was hesitant as I didn't see how they would do any good, just keeping your palms warm. Man, was I ever wrong! Heat the palm, and the inside of the glove stays warm... I go all winter with just a thin pair of gauntlet gloves to keep the wind from blowing up my sleeve.
Only time I got a little cold was last winter riding the freeway for an hour, and then it was only my thumb tips. It was 20-25* that night, so you true polar riders may have different experiences.
The nicest thing about them is they always there. No cords to run down your sleeve, nothing to plug in, and nothing to forget at home.