Haven't tried of of this stuff either, but I have seen a lot of good comments on forums such as Camaro 6 (cosmetic maintenance section) on different coatings. A lot of vehicles have come out much shinier, though a large portion of it was from good ole color sanding & buffing first before application.
I did have 1 detail guy pm me after seeing me comment on a thread & from seeing that I did some cool custom work, gave me his thoughts on the stuff he used in his business & got fabrication advise from me. Being that was someone not being paid a cent to give me product advise, as with most spi advise, that would incline me to give it a little more consideration for a new vehicle with thin ass cured paint that will be daily driven in harsh stuff, but definitely NOT YET for something I painted.
Guy I mentioned hadn't heard of painting issues with the ceramic based stuff, as he had also done paint correction on repainted parts for his regulars.
Now there were some silicone based products years ago I've heard of many cases of they soaked down into the metals & infinitely ruined the car for even repeated future repaints. I think most of the modern products don't penetrate the surface much more than a repaint would.
That's about what I know, which is not enough for a firm decision either way, still leaning toward eh??, though more open minded.