I have been using this for a few weeks and couldn't be more impressed.  Dull knives are always driving me nuts in the kitchen, but having this I can quickly and easily sharpen a knife and get back to cooking.  10 sweeps in the sharpener, and the knife is good as new.  It seems to work best with Ninja chef knives, but I've used other brands with similar results.  Lastly, this sharpener isn't bulky and can fit comfortably in a kitchen drawer.