Pros: easy to use, inexpensive, does the job
Cons: none for me
Are you just happy to see me or is that gleam in your eyes because you just polished your glasses with Rain-X Glass Treatment? Well, that may be pushing the envelope a bit, but Rain-X has become a staple in our home. When we had our frameless glass shower doors installed we asked the manufacturer agent the best method of cleaning this massive surface without streaking. He told us to get Rain-X and apply it once a month.
Since patented in 1972, Rain-X has been beating us over the head touting their stellar abilities on the windshield of your vehicle. According to their hype, spray the product on and you will have better all-weather visibility and safer driving conditions. Which begs the question: if their product is as good as they say, why do they also make windshield wipers? These are just things that pass through my head. Personally, I've never used it on the windshield of my car, so I don't know from my own experience if it works or not. I've heard things both good and bad about that subject.
However since they also recommend use of the product on glass shower doors and home windows, I do have experience in that field. We spray it on the surface of our shower door once a month and the water simply beads up and rolls down the surface. We then use a squeegee to swipe the surface free of water beads and we are done. No bothersome streaking like you find when you use a product like Windex on a large surface. It just seems like you can't ever beat that streak effect. The surface has to be dry before applying Rain-X.
You cannot use this product on any plastic surfaces, solar panels, plastic shower doors, or any shower doors with etching or frosting, plexiglass, and fiberglass.
According to Wikipedia, Rain-X's primary active ingredient is hydroxy-terminated polidimethysiloxane. But according to the MSDS sheet for Rain-X, they list the ingredients as: Ethanol 60%, Acetone 30%, Isopropyl alcohol 30%.
Health hazards from the product include but are not limited to: irritation if inhaled; skin dryness and cracking with repeated exposure; irritating to eyes on contact; harmful if ingested, could cause lung damage; possible organ or organ system failure with prolonged contact. In other words, use responsibly and keep away from children and pets.
Rain-X makes many other vehicle related products: headlight restoration, wiper blades, waxes, washer fluids, and bug & tar removal products. I have not tried any of these so I cannot pass judgement on them.
All I know is it works fantastic for our glass shower door. About the last week of the month we notice a tad bit of streaking when the water doesn't bead up like it does at the beginning of the month and, frankly, it works as a reminder that it is time to treat again. Application is easy and fast and it lasts a long time. I just wish it would work on the dog nose prints on the interior windows in our living room.
Oh ... there is also this - WARNING: This product contains chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. What about the rest of us?
 copied from Amazon.com website, not my own words