|>>|| No. 2441
I'm not him nor have I used one of those monstrosities, but since it's a whetstone that does the angle for you, I can say that it'll razor sharpen a dull knife in a minute or two, and you can absolutely rescue dinged knives by grinding away on a coarse stone for a while then gradually using finer stones. That might take a while, depending on how fucked the knives are, but probably no more than 20 minutes for civilian damage, and it's quite a zen process.
There are still knife blokes who seem to appear in cookware shops on certain days who will regrind your knives proper. I don't really understand who they work for or why they only charge 2 quid a knife, but if you run into one get him to work his magic.