It won't effect the wipers working no...
All it does is act in the same way as wax does on paintwork. It helps to repel water and stop water from settling on the surface of the glass. So, at speed, rain drops just stream straight off the screen meaning that you have better visibility so don't need to use your wipers as much. It's more noticeable at higer speeds, the stuff I use really starts to make a difference from about 50MPH upwards.
It looks pretty cool when the water drops are all whizzing up the screen.