They do come in handy in the snow/ice, but also while driving and you notice a large bug shaped dim in your headlamp beam pattern. I don’t have them on the Prius, but on the Lexus RX they work well.
The best system I have seen though was on a Mercedes (I think) where it had heated/steamed sprayers. That really helps with the snow ice. If I had them on the Prius, I would probably add an aftermarket conversion to electrically boil the washer fluid right before shooting it at the lens.