I've got one, but I don't use it a great deal. It works very well for restoring trashed serrations. The 600 mesh feels about midway between DMT Coarse and Extra-coarse. It will remove steel pretty fast, with little pressure needed. The variety of surface shapes make it useful for any number of sharpening chores, especially if you are already skilled at freehand sharpening. As far as guided sharpening goes, it produces an edge angle of about twenty degrees per side, and only on the corners, so it leaves a pretty coarse edge. I'd like it better if it was set up to do 15 degree per side back-bevels, but that's life.
It's a bit large to be pocketable, but it would make a good backpack field sharpener.