Leah,
I know of several coach owners who have had it or a similar material installed, and they were all happy with it, except it was expensive. From my experience, If you have an issue with leaks in your fiberglass roof from porous fiberglass or hairline cracks from hail damage, Roof Armor or a similar bed liner material is the only way to correct the problem. However, if you are trying to protect the gelcoat (white area of your coach roof) and prevent excess white streaks down the side of your coach, the most economical and efficient method is to just paint the roof with something like Rust-Oleum Topside Deck Paint.
Gerald