I’ve never liked those. They can chip a blade, the angle is very wide. And they remove metal in such a limited band so close to the edge you rapidly lose the overall geometry, leaving a knife that can’t be sharpened without some re-profiling. I have a pocket knife from a friend that used one of those religiously, and it took a lot of grinding to get an edge on there after he’d used the Lansky for a just a couple years. I needed to thin things out and put a completely new bevel on there.
On the plus side it taught me a lot about sharpening.
They work very well for touch ups, pretty common in meat processing/butchery and the default thing for fish mongers. But they aren’t a substitute for proper sharpening.
