This device is nearly foolproof, if you follow the directions on the inside lid of the case, and the edge you get very long-lasting. You also get a sense of intense personal satisfaction when you know that you, personally, put your favorite tools back in tip-top working order, and for a very reasonable price, in money and time spent. I do my sharpening while watching DVD movies.
I think GATCO has the best, most versatile sharpening system. Kitchen knives are used for different things, and within those applications, often call for different angles of sharpening. For instance, boning knives, filleting knives and cook's or chef's knives all should be sharpened to different angles, not to mention cleavers. GATCO can do all of these, as well as serrated (albeit with a special hone).
As to "sharpening" steels, when I was in Cook-Chef class, I was taught that "steeling" a knife was for the purpose of aligning crystalline molecules of a knife's sharp edge, thereby re-strengthening the factory or stone-achieved edge. Wether it was through friction-induced magnetism (as is my personal conjecture) or not, I do know that excessive steeling does produce filings on the steel and the knife's edge.