Recent drives in the rain have led me to believe that all rain sensors are crap. I had them years ago on a 206 and didn't think much off them. I thought that time and a better brand might mean these ones would be pretty good but no.
The variable non-sensor system in my old golf was much better. I just find that the sensors tend to have hissy fits now and again and put the wipers onto full blast. I personally think they should go no further than standard wiper speed. Who ever uses full speed anyway - maybe when passing a truck when there's a lot of spray, but otherwise never.
Also, fiddling with the sensitivity has very little difference.
The light sensor on the other hand is excellent.