@Jethro - I remember that. It was just after Kathy and I had driven from Washington DC to the bottom of South Carolina in an F150, at night, in a torrential downpour for 7-1/2 hours - Thankfully, I wasn't trailering Pearl on that trip.
Rain-X all the way with no wipers if we were over 30mph. I had to stop at a TA truckstop halfway through for gas and re-applied the Rain-X, but it worked great. It was actually clearer vision above 30mph without the wipers sweeping than it was with them going, but I figured the trolls who jumped on you would never believe that so I just kept quiet.
If you apply it properly and have enough speed to allow the water to stream off, Rain-X works great. If you think you'll have perfectly clear vision below 30mph without enough airflow to push the water drops to a film you'll be disappointed.
I apply it every Spring to the Speedster...and then never go out in the rain - But'cha nevah know........ 