I did my trailer with it, basically ignoring their instructions, kind of as a test to see how it would work.
I used "expanded metal" on the trailer, so it is very hard to coat, hard to prep, and hard to cover well. The metal was as bare as it came from the metal supplier (probably had mill scale on it) but had been outside for a year or two, so some decent rust forming, but not really pitted, just a light surface coating.
I just brushed the paint on thick so it would run into the places I missed, and left it at that.
After about two years now, it is still sticking to the trailer no problem. No large flat surfaces though, so peeling issues probably aren't going to be seen in my case no matter what.
Definitely affected by UV. It lightened up considerably (I think I got semi-flat black, or flat if thats all they offer, I know it isn't gloss) but that didn't seem to weaken it any.
I don't personally believe it's a miracle paint, I've also tried one-step I think it was, and wasn't really impressed with it. I'm of the opinion that there really is no "magic paint", since every application is likely to be different in one way or another (humidity, temp, prep, application technique, material painting, etc.) results probably vary with every use.
I'm not saying I don't like it, but I'm not sure that a rattle can, or another brush on product wouldn't work any better.
For home-applied coatings (of any type) I think we still have a LONG ways to go before we are able to protect things like manufacturers can with ceramic coatings, urethane dips, and so on.