I used a turbo visor for a short while,good for riding in heavy rain and snow it was always clear, not a lot of noise from it either, mind you if you have a gold star exhaust on your bike you don't tend to hear anything else !
The big problem was if you turned your head or tilted the thing up it could come off the helmet, also it let quite a bit of wind round onto your face. But the main thing that made me stop using it was folks laughing at the thing plus the mockery from the girls at work, it had to go!