RE: Rain X
There apparently is one drawback to Rain X according to the shop that did my
windshield replacement.  If you have used Rain X they can't do the rock chip
repair thing.  Rain X is a silicon based product and once it's on the glass
(and seeps into the cracks in the rock chips) the polymer that is used to
fill in the rock chip/bullseye type damage won't adhere to the glass.  I was
also told there was another product on the market that did the same thing as
Rain X but didn't have that problem.  I don't remember the name and I've
never looked for the other product.  And that's the only time I've heard
that caution.