I have been using rain x winshield washer for few years now and i donot seem to be haviing these spots you are talking about.
gary

 

I tried meguires plast-X or whatever its called, the plastic polish got all my water spots off the glass! I finished the job with some invisible glass.

 

i seen some shops do this. they use like really really fine sand paper and wet sand it. dont see anything damage to the glass

 

I just use some of my paint polish and a yellow CCS pad on a hand applicator. It seems to get the fresh waterspots off the glass no problem. Since I already have the stuff on hand for my paint, I don't have to spend any more on supplies.

I usually follow up with some Invisible Glass to reduce the shine the paint polish leaves.