Yes I have ended up pulling the head periodically and have _never_ seen an issue with the coatings. I think 0.5-1mm thick coatings would be a whole different issue (and not a good idea for this application), and none of the mainstream coating suppliers do that to my knowledge.
Not sure on the higher temperatures comment -when I was running the Elgin cam and prior to switching to E85 I was seeing EGTs in excess of 1850 degF - still no issues with the coatings, but I did end up dropping an exhaust valve seat. Even this did not cause flaking on the coatings, but they had to be re-done after the resulting head work. I did follow up with Ferrea "super alloy" valves rated for higher temps and more extensive coatings, as shown in the pics.