Those PIAA's sound pretty slick. But, I've always found the stock BMW ones to be really good. I think part of it is keeping your window clean. I recently did my aunt's X5, which was SOOO SOO bad. There was a thick film of sap and road crud over her entire front windshield. When it would rain the water would just spread out and visiblity was aweful. Her idea of getting the car extra clean and protected is to pay a few extra bucks for the DuPont Deflon goop at the machine wash. (Who knows, maybe that was part of the crud on her windwhield.)
Anway, I used ClearGlass and newspaper a few times to get it clean, then did two coats of RainX Window Wax (not so much for the beading properties, which I think disappears very quickly, but for the extra cleaning). Now her old stock BMW blades are like SUPER DUPER blades.
The window just needed to be thoroughly cleaned.