We have a machine at work that works off of the same theory. We use it to polish EDMed surfaces to a mirror like finish. It will slightly round sharp edges if you aren't careful. We use it on hardened steel.... usually Rc 56-58.
Correct, these work in the same way as EDM (Electronic Discharge Machining) does, EDM's have been used in the building of hard steel injection mold making for decades). I see this as a cool new way to do a dirty job. Someday the prices will drop and we can have one in our tool boxes.
