Logres, how are you coated headlights holding up?
After a close inspection, I am starting to see where the coating is chipped off, but there is still 99.9% coverage. The only way I really knew the coating was still there was that I accidently scraped a tiny bit off with my newly cut fingernails...so that's a good sign. The largest chip measured 1/8" x 1/4". The underlying plastic was flawless, so it must have just happened. The chipped area was not yellow, unlike the coated area which has yellowed slightly, like a typical 5 year old headlight, which means the coating took the brunt of the UV light. It should be noted that this coat is a couple years old, so I've exceeded the manufacturer's recommended specs (I think they recommend a yearly reapplication), and it shows. It does need to be cleaned off, prepped, and recoated.
All in all, I would say that using this stuff is marginally better than not using it at all simply because it requires the same or more amount of work as just sanding the headlight every couple years. I've decided to keep using the coating simply because it keeps UV light from the lens - the impact resistance is neither here nor there...you've got to sand it off anyway.
The overall best solution is a plastic cling film like Lamin-x. It is invincible to impact and UV light (won't chip or discolor) for 5 years. But my local dealer quoted parts and installation at $300 for the Mark, so it aint cheap. I'll continue to coat until something better comes along.