It is something I do fairly often. And think about even more! My wife runs a commercial Lawncare business so I have plenty of opportunity.
I currently sharpen in a big vice, with the 7" grinder. Grind the blade straight on the face first, remove the back side burr, then grind the angle onto the front. Burning occurs occassionally when I get in a rush. Light cuts and a practiced hand make it go pretty quickly.
I have been eyeing a Magna Matic for the last several years, but the price covers an awful lot of my time.
A bench grinder is not the same, as it is a low speed wheel designed for high removal speeds.
It really comes down to how much you are sharpening blades. My case is I should do 12 blades every other day or every third day, and realisticly do the 12 blades once a week to week and a half. I teeter on the brink of it being cost effective to buy the Magna Matic in my opinion. Anything less I would not bother, anything more and I am shelling out the bucks.
Soundguy, I have looked at those wheels, and cannot picture them doing anything but "dressing" which may be what you are saying, but for me, it is quicker to have a good sharp set, reach under the mower with the burp gun and swap them out.