Warthog Multi-Edge was originally designed for Knives, but has been better served as a chisel, planer blade and scissor sharpener because is does have infinite angles between 10-90 degrees. and i agree, it is a bit of a contraption and i do find it difficult to stabalize while sharpening.
Warthog V-SHARP has 2 models (1 Metal & 1 Plastic) both sharpeners work the same but have preset angle adjustments of 17, 20, 25, 30 (filet, kitchen, pocket, meat cleavers). what makes the V-SHARP work so well is that it combines equal pressure and constant angle, while you pull your knife through. you can Google "vsharp" to find the website and videos to see it in action.