Well £15 for a piece of tiny glass is just ridiculous IMO, i used a £1.70 grommet and some silicone, no leaks, no holes etc, its a perfect fit , and with reference to what its like on a wet day,, well you cant see much, but i just use the wing mirrors!!
I would much rather have the clean look on the back than a wiper blade, and its comign up to summer so only thing to worry about hopefully is dust on the back screen!
Dan