One of my customers have one and i had the chance to test it.
Well, how to say... For someone who never touched a stone, or is not willing to learn how to do so, horl can be ok.
However, with the given kit stones, you wont go far, and you need to buy the extra finer grit set. Which in the end will cost you more than 400, 1000 and 3000 naniwa chocera stones...
Morever, the life expectancy seems... very very short...
I tried on a gyuto 240mm x54mm tall heel, and it didnt fit, the blade was too high...
Very difficult to properly sharpen the tips, and if you apply just a little too much pressure, the blade snaps off from the magnets.
To sum-up: Good for old little grandmas, or anyone who has money and dont want to learn sharpening on stones.
Bad for everyone else.