I had the Wonderwood years ago, and I loved it as a heater, and the simple bimetal thermostat worked very well. It put out plenty of heat and with it's circulator design I never felt I needed a blower. The "only" problem was that, at low burn rates, it made tremendous amounts of creosote and I had one chimney fire and one creosote-plugged chimney cap that sent me scrambling up on my roof in the middle of the night to clear it. My understanding is, the difference between the Wonderwood and the Wondercoal was (1) shaker grates and (2) a modified loading door with secondary air for the coal. It may at that time have had a gravity-latch load door rather than a positive lock, so it could blow open if you had a coal explosion. The current design has a positive latch.
I would not hesitate to try a Wondercoal in the garage for burning coal, but I personally would not use it for wood, I'd use one of the newer wood stoves specially engineered to meet EPA specs.
Here's a fun story about the circulator feature -- that is, the double-wall construction that acts like a mini-chimney to whoosh the heat out the top of the stove. One of my kids had a mylar balloon that had lost a lot of helium so it just hovered a couple inches above the floor. I held it above the stove so it got nice and warm and the helium expanded and filled the balloon, then I let it go. As the helium cooled over about five minutes, the balloon gradually sank toward the floor. But as it sank to different altitudes it followed the convection currents all through the house. First it shot to the ceiling above the stove, then migrated across thirty-five feet of ceiling to the far corner of the living room opposite the stove's corner. Then it cooled a little, sank a little, and migrated fifteen feet from the corner to a door into the poorly-heated kitchen. As soon as it cleared the kitchen door it shot to the ceiling again because the kitchen air was so much cooler. Then it migrated thirty feet tacross the ceiling o the far corner of the kitchen, sank as it cooled, and migrated at lower altitude following the air flow returning to the living room. By this time it was cooled almost completely and it made a beeline across the living room floor straight back to the stove.