The DLC (Diamond-Like Carbon) process creates a thin surface carbon layer made up of amorphous (non-crystalline) carbon atoms. If they were crystalline, the surface would be clear - like a diamond
In terms of mechanical toughness, the surface is very tough. If you took a metal key and scratched the surface, the scratches are the key being eroded by the DLC. Of course, if continued, the coating will eventually be rubbed off as well.
The coating is not very thick, so the steel underneath which is relatively soft, still deforms under impact. But light scratches should be easily polished out by licking your finger and running it over the offending area, no sweat.
I'm investigating TiAlN as a possible surface coating, combines the toughness of Titanium AND Ceramic, it's used for certain high strength coatings and has a deep lustre which looks IMHO better than DLC. We'll see where it goes...