Check out this Winshield!
When I bought my '99 323i, it had all BMW glass except for the windshield. I noticed that Pilkington, local to the Toledo, OH area, and one of the largest glass makers, had their name on the windshield. Now, I don't have the rain sensor (nor do I think I would want it), but I noticed that when I drove in the rain for the first time a couple of years ago, it seemed to have Rain X on it or something, because in torential downpours I NEVER have to turn my wipers on. Come to find out, over 2 years later and NO coatings of any sort, it STILL is like that.
There appears to be some sort of "magical" permanent coating on the windshield that makes it do this. I know for a FACT they do not make an applied coating that lasts over 2 years...and we have hot summers and cold winters. I haven't done a lot of research on this windshield yet, but I would certainly advise checking it out if you need to replace one.
It's so cool to be able to do 80 MPH in a torential rainstorm, passing everyone on the expressway, WITHOUT MY WIPERS ON.
Officer: "I see you set the table for four." Groucho Marx: "That's nothing--I set my alarm clock for eight."