I'm not convinced, Greg. I used to buy blunt blades and use them as-received, but they would not cut one particular kind of "grass" that consists of very small diameter cylindrical blades that grow one-per-plant from a largish underground nodule. Sharp blades will cut that stuff, and if you keep it cut, it doesn't seem able to compete with the real grass, so it goes away. I've been using sharp mower blades ever since.
Incidentally my slasher (a 5 foot offset contractor type with a 70 hp Hadbro gearbox, I don't recall the brand of slasher, but it was one of the 2-3 serious local brands) had sharpened blades, and it is just as well, considering they were half inch thick spring steel, two inches wide.
I agree that you can do most mowing with blunt blades, but you can get a neater job with less blade speed (and therefore less machinery wear) if you use sharp ones. Ordinary push-mower blades can be resharpened with a hand-file in mere seconds per blade, without removing them, if you maintain them. For me that means a touch-up about once per 2 years. If you tend to mow a lot of rocks, it all becomes more of an issue though.
