I've had USCCA for two years now and thankfully haven't needed anything from it. Their online scenario-based training is very good, as is their monthly magazine. But no, I don't know of anyone who has had to use them, apart from their own published cases.
There's a certain amount of faith involved in using any of them, since none have the kind of established history of a typical insurance company, but it seems unthinkable to me to not have it (assuming it works!) because even the price of being found innocent can be staggering.
My favorite online trainer dude just made a video about why he finally picked up CCW insurance, and it was USCCA, and he's cool, so I guess that's good enough for me
https://warriorpoetsociety.us/uscca-review/