A rambly update:
I got both of these, but never actually tried using the PWM.
The heating pads got pretty warm at a slow speed the first time I tried using them, but not after? Not sure exactly why. The last time I used them I got a random hot spot on the tip of my pinky.
They helped a lot compared to no pad, but they weren't a great solution -- they bunched up, felt odd, left lots of cold spots.
I got the Gerbing heated gloves that prompted this all for $37 from an overstock store. Everyone was saying that they really needed the temperature controller, but they're pleasantly warm when I'm sitting still, and perfectly neutral at speed. So I don't understand why you'd want to turn them down.
Now the same trip that would have had my hands painfully cold in 30 minutes at 30 degrees going 65mph feels entirely fine.