I have sharpened mower blades many different ways over the past 35 years, file/bench grinder/right angle grinder. They all work ok but it can be challenging to maintain the same angle all the time plus with low RPM grinders it is easy to overheat/burn the blade loosing the temper causing the blade to dull prematurely. Commercial blade grinders are costly but do eliminate improper grinding angles also turn at a higher speed pulling metal off quicker pulling the heat with the metal particles thus keeping the blade cooler. I would have to agree that it would be impractical to own a commercial grinder for my own purposes but with that said I have taken on sharpening jobs around town looking at a three year payback on the sharpener. I also bought the balancer/truing gauge. I would agree with others that vibration is not as noticeable with two or three blade decks, but I have personally witnessed a large single blade Honda self-propelled walk behind mower that was without a doubt night & day difference after balancing at idle or full throttle gauging the vibration/shaking on the handlebars. Here again I probably could not justify a balancer without custom sharpening/balancing blades to offset the cost. After a season of operating my sharpening business I am able to an A+ sharpen & balance on a blade in an average of slightly over 1 minute. I do know a larger lawn care service that owns their own blade grinder and balancer.