I have one of those and have only used it a time or two. Basically, it seems to be the functional equivalent of an umbrella. Meaning if the wind isn't blowing and you go slow, then you can stay reasonably dry on the upper part of your body. Go too fast, or have wind, or stay out too long, and you're going to get wet anyway.

i've ridden a time or two when it was in the 70's and raining and the simplest solution was just to get wet and be done with it.

I've not been out in cold rains, but the rando guys tell me best solution is to try to stay warm rather than dry- so something like rain jacket with wool underneath.