I will gladly admit that Rusty has worn a choke collar for years. However, it was only because he has a huge neck and knows how to remove collars...but for some reason, he didn't even try to get choke collars off. Nylon collars, leather collars, harnesses...you name it, he can get out of it. Choke collars, though, he didn't seem to care about removing. So that's what he wore for a long time. It wasn't until recently that his choke collar broke(I have no clue how), and I have yet to get him another one. Right now he's in another nylon collar, and surprisingly enough he hasn't tried to get it off. And yes, I've checked to see if the collars are causing him pain or discomfort. They weren't. He's just quirky, lol.
Anyway...personally, I have used one. However, I didn't clip it to the ring. I clipped it to the chain itself. The danger with this is that it can easily slip over the head. I think clipping it to the chain is not as bad as clipping it to the ring. I don't use them as a form of training at all. Rusty's was/is simply just because he doesn't get it off, despite the fact that he could. I prefer other, gentler methods.
I'm not a fan of prong collars either. Many puppy obedience classes strongly support prong collars, but I don't like them. Yes, I have put one on my arm and pulled it. No, it doesn't hurt. But try putting one on your neck, a much more sensitive area. Especially high on the neck, where many trainers suggest to put it because that area is the most sensitive. It's extremely uncomfortable, even painful.
Neither the prong or choke collars are always successful. Many dogs will continue to pull, leaning into the collar, which only makes it worse. When used on young dogs, it can severely damage their tracheas if misused. Too many people buy these tools without having a clue how to use them.