Copper and silver ions in your pool means difficult to remove stains on your pool surfaces and potential green hair if you don't watch pH levels like a hawk! Eventually copper and silver ions get high enough they will stain and turn hair green no matter what the pH level is.
Well someone recently disclosed that I was wrong about these, they do in fact work quite well at putting copper in the pool. Which is why their pool was covered in copper stains which they were desperately trying to remove and forced to dump a bunch of water to reduce the copper levels. I used to think they didn't add much copper at all, so that proved me wrong there.
So they are an expensive way to add a metal to the pool which you don't want. Copper is the second worst thing you can add to a chlorine pool and the industry's obsession with it makes me queasy. Following TFPC keeps algae at bay with no side effects, there is never a good reason to add copper to a pool.