I bought three of these too, but didn't get the course one. Should I get the course one as well?
I don't know what properly sharp is, so I watched Paul Sellers' video thing and tried them out on a chisel. It came out much much sharper than anything I've achieved before. I couldn't see any wear at all on the plates and there's no way the plate won't stay flat. The video says to use glass cleaner, which I had to hand, so I did.