It does sharpen knives quickly. But it's just a couple of grindstones, no different to those found in a workshop. So the idea that the second slot "hones" is a wee bit of poetic licence. It's just a finer grindstone.
It's very easy to produce a wavy looking blade if you use too much pressure, but that's probably true of any similar product. Read the instructions carefully.
But as to claims that it produces a razor sharp edge, well ... if you think that then I wouldn't want to try to shave with your razor.
It does seem to grind a lot of metal off into filings, and it's not too good at catching them all. So a fridge magnet (that I didn't have) would be a useful gadget to have around to pick up the metal filings. To be fair, it probably doesn't produce any more metal filing waste than any other similar product either. It doesn't leave piles of filings behind, but I could feel them on the work surface for days afterwards.
But at fifteen quid it's a very good deal. Knives do come out sharper than any other method that I've tried. But that might be because I'm not very good at sharpening knives.
I wouldn't have been too happy had I paid fifty for it though. And I'm wary of using it often because it does grind away a little bit of the blade each time you use it. That's probably true of every method of sharpening knives, it's just easier to grind a lot away with a grindstone than with a sharpening steel. But I can't use one of those either, so this product is probably the best method I'm going to get. Certainly at this very good price.