I bought this in April, 2010, at my local HF store. Normally $70, they were on sale for $60. And in the advance sale flyer they handed out, there's a coupon for only $50, valid in a week or two.
I also bought a package of 2 spare wheels (one diamond, one emery) for $10.
I searched the web to see what other people had to say about it. Mostly I just found postings asking for owner's opinions. I did find one page on a welding site describing using one for sharpening metal-cutting cold saws. He said it worked out quite well. The next step up that I've seen in circular blade sharpeners suitable for a home shop is on ebay from a couple of sellers in China and costs about $400 ($270 + $130 for shipping). It looks like a substantially nicer machine from what I can see in the small pictures. I'd sure like to try one. (Donations to the fund will be gratefully accepted!)
First of all, I'd say the sharpener is easily worth its price. It takes a lot of experimentation and learning and practice, and quite a bit of setup time converting from one tooth angle to another. And its tooth alignment registration stop pawl is tricky to adjust for the right grinding wheel cut on the tooth. It badly needs a fine adjustment mechanism of some sort. The knob that holds the blade-holder arm in position is hard to get tight enough. The pivoting arm that the blade tooth registration stop slides on needed to be smoothed with a file, and moving the stop is still a bit jerky. Changing the grinding wheel is made a bit inconvenient by the 3 small screws that hold the wheel guard side onto the rest of the guard. So far I've been leaving it off while I'm experimenting.
The instruction manual is minimal. The parts are not well identified and there is no picture or drawing of the machine set up and ready for use. There is no information on actually sharpening a blade. You have to already know how to use the grinder before you get it, or else teach yourself to use it. It might be nice to have an old scrap blade or two to learn on. It's not really too bad, though, because it doesn't take off much metal at one time, so you're not too likely to totally ruin a blade. It does take a lot of fiddling to get the angles set right for the bevel angles and to get the cutting edge of the tooth parallel to the wheel.
But the machine is a lot handier than trying to keep consistent angles with a file as I go around a circular blade in a vise. And it does carbide. I know - I can use diamond hones on carbide tips, but that's really slow. And it's hard to keep the tooth surface flat.
So far I've had the grinder for about a week and I've used it on three steel blades and a carbide one. I can't sharpen the sloping top of saw teeth. The grinding wheels just work on their edges. Well, the diamond one for sure, because it's a very thin steel plate. The emery one might be usable on its rim but it's very narrow. The wheel tapers to a thin edge on the outside or right hand side. In the instruction manual is a diagram showing grinding the top of a blade tooth with the edge of the wheel, but the wheel shape in the diagram is not the same as the wheel with the machine. The rim of the wheel would need to be a bit wider and beveled instead of thin and rounded.
If you're not already quite familiar with sharpening principles like clearance angles and judging surface flatness by the bright spots left by filing or grinding, don't buy the machine. If you can't teach yourself or you don't want to experiment, learn and practice then don't buy the machine. If you're in a big hurry to get your sharpening done, don't buy the machine.
But if you are patient and like learning new skills, then it's a fun and rewarding purchase.
I recommend it.