I, too, have found Rain-X to work well on windscreens and rear windows, and I also apply it to the headlamp glass. I've tried both the original rain repellant, after cleaning the glass with the Rain-X cleaner, and the 2-in-1 Glass Cleaner with Rain Repellent. The original is much better, in my opinion, staying good for 6-8 wet weeks and, if you are moving relatively quickly, delaying the need for wipers as the water simply beads up and runs off, driven by the air moving over the car. Its less good in stop-start conditions, but still means you need less wiper movements and the glass cleans very well after a single sweep