Belt sander sharpening is like anything else- you wouldn't drag your blade edge perpendicular across your stones would you? Well if you use a little common sense in belt sander sharpening you don't need to mess up your blade either. It is quicker than hand sharpening, and it produces a very nice edge. Because of the geometry of edges the convex edge produced by the belt sander will not be as sharp as the flat grind you produce on a stone, but when sharpenend correctly I don't think the average person would ever know the difference. There is certainly a learning curve on a sander and the first few knives may be damaged. It definitely has the potential to do that. But I would say that once "mastered", a belt sander is every bit as valid a sharpening tool as all those spendy stones.
