I used Rain-X for many years and have no complaints about it. I mostly don't now because I simply don't have time to clean my windows often, much less do a Rain-X install.
What I have noticed, is when washing my windows, using paper towels I can never seem to get them "film-less". The only thing I've used that works is a squeeky clean cotton shirt or sock. Almost every paper product I seem to use lets a film, but the cotton cloth buffs it right off. Not sure if it's the window cleaner (Windex, et al) or the paper chemicals. Could be the reason some people have trouble with Rain-X.
"It`s not important that you know all the answers, it`s only important to know where to get all the answers" Arone Kleamyck
"...An unarmed man can only flee from evil, and evil is not overcome by fleeing from it." Col. Jeff Cooper
Sunset Creek 298 BH