some pithy "knife sharpening 101" videos: [1][2][3]
some videos that demonstrate his tremendous expertise: [1][2]
He thinks the rolling sharpeners are good for people who want a fairly no-fuss way to just get their knives sharpened. [2] (note that the Horl 3 is going to be released soon, but I don't know that its new features are worth the big cost increase)