I bought one in a moment of madness, helped along by the three year warranty!! they actually work reasonably well, and will put an edge back on a drill that will drill steel no problem, but can be improved upon with a bit of off hand work. The same cannot be said for the set of drills which comes bundled with the sharpener, which seem to be made from tin coated putty! The fact that they come with a spare grindstone leads me to believe that the stone will wear out fairly fast, but you do get the whole lot for under £20. I also bought a set of metric drills in a metal fold out case for £11-99 or thereabouts, they are my only set of metric drills, and I have not had to sharpen one yet, but they are used mainly in a drill press, which helps.
Phil