I bought one, and I have used it a little. Frankly, I'm not terribly impressed. I suppose it would be all right for serrated blades, but I seldom use those enough to require field service. I found it rather awkward to use as intended for plain edges. Coupled with the fact that it takes up more room than a pair of two-sided DMT Diafolds while offering a single rather coarse grit, makes it a paperweight for me.
I might well have a different opinion if I didn't have over thirty years of experience freehand sharpening on benchstones. For someone who relies on a guided system to sharpen, it might be worthwhile as a field sharpener. Personally though, I'll stick to my Diafolds.