RainX sux... I have tried Liquid Glass and Zaino Z2 on my windshield. While I find it excellent for the side and rear glass, I find that the wipers rapidly degrade the polymer coating on the windshield and leads to some smearing after a while. Some people don't use their wipers with them coated, but I find that I need to wash the bugs off. They tend to smear more with the coating on.
Last treatment I gave the windshield was Zaino Glass Polish with a PC and left it just like that. The glass repels water, but not quite as good as with the Z2 coating, but there is no smearing with the wipers. I use Eagle One 20/20 with a plain old terry cloth for fast and easy maintenance. I used to use Stoners, but find EO less prone to smudging and leaving a haze. Some say that EO imparts a "RainX" like effect which causes water to bead. I am not sure if it is the Glass polish or the EO, but the water does bead slightly....not as much as RainX or Z2. Trade-off....
H