This is just off of Wikipedia;
Applications of DLC typically utilize the ability of the material to reduce abrasive wear. Tooling components, such as endmills, drill bits, dies and molds often use DLC in this manner. DLC is also being used as a coating by some weapon manufacturers/custom gunsmiths. Some forms have been certified in the EU for food service and find extensive uses in the high-speed actions involved in processing novelty foods such as "chips" and in guiding material flows in packaging foodstuffs with plastic wraps. DLC coats the cutting edges of tools for the high-speed, dry shaping of difficult exposed surfaces of wood and aluminium, for example on automobile dashboards.
One thing I have noticed with DLC is it tends to drag when cutting certain foods, there is more resistance when you are say cutting an apple than there is with an un-coated blade.