Since we have had some early snow and ice here in Virginia, I've been able to test the Prius anit-skid systems. I hit the brakes on an icy parking lot, and it very quickly unlocked the wheels and displayed the "overriding inputs of stupid human" symbol. Another time, after exiting the driveway, I gave it a bit of a turn and stomped on the gas. It stopped the skid in probably less than 1/6 of a tire rotation, and gave me a speed that would maintin proper traction. Quite an impressive system.
I haven't gotten into a situation where it brings me to a dead halt, as on a totally icy hill. I suppose, in that situation, I would wish for an override button.
Paul