Recently I was driving the TF in heavy rain it was on an A road and I was keeping up with traffic at about 50/60 mph, I discovered the wipers only needed to be on slow and was mesmerised by the waves of water traveling up the screen horizontally and disappearing up and over the roof. I thought "I wonder if" so I did and turned the wipers off (not advisable) it made hardly any difference the air over the screen was capable of clearing most of the rain.
I have never noticed this on any other car I've owned but will qualify that by saying the TF probably has the most steeply raked screen of any car I've owned, have other people noticed this on the TF or experienced it on other cars.