I dont personally but farrier who does work horses has started by chance as they sent him the wrong ones, and my farrier uses them with a handful of his horses. Work farrier is just getting round to 2nd set of shoes with them, has changed 1 set and said he thought there was a slight improvement in the nail holes.
My farrier uses them for horses on his books with ongoing problems,he does alot of remedial shoeing and he says they have being making a difference to the ones with poor horn quality and problems with WLD and he is confident it's the copper nails helping so is carrying on using them with horses he feels will benefit.
Both said it adds a few £ onto a shoeing so nothing extortionate and definitely worth a try in their eyes.