This is a great product.  It's reasonably easy to apply and it works well.  Why only 4 stars? I'm unfortunately fairly lazy with stuff like this.  I get inspired, clean the windshield, apply the Rain-X, enjoy the incredibly clear view for a while.  Then what happens is the product starts to wear off and actually your windshield gets worse than it would be without Rain-X.  The rain drops seem to actually stick in place, like the surface gets addicted to Rain-X or something.  So anyway I often don't get around to replacing it until months after it needs to be re-applied. This means that although my windshield is perfect for a month or two, the average clarity of my windshield might be considered worse than if I had not used Rain-X at all.  That said, it does an excellent job if you keep on top of it.  If you use an inexpensive micro fiber detailing cloth to clean your window just prior to applying, it's really pretty easy to put on.