I've both fermented and served kegs in my chest freezer (keezer) controlled by a Ranco, though not at the same time.
The Rancos are pretty easy to use, especially if you order the wired one, if you don't you can wire it yourself with a heavy extension cord from the hardware store. The later is cheaper, which is why I went that rout. You can find info on wiring the one stage here, and the two stage here. They do just plug right up. The Ranco is plugged into the wall and the freezer is plugged into the Ranco. It is then the Ranco's job to interrupt power to the freezer in order to maintain your desired temperature.
If I'm using the Keezer (by the way it is the Magic Chef 7.2 that will hold 4 kegs w/o a collar as seen in this thread) for fermenting then I will tape the Ranco's probe to my glass carboy for a more accurate reading and set the controller for the ferm temp.
If I am using the keezer for kegging I set the Ranco for 35 degrees, I know that is cold but that is where the condensation freezes to the sides of the freezer walls instead of puddling on the freezer floor. The condensation is just part of having a manual defrost freezer. The condensation doesn't seem to be a problem at fermentation temps though.
If I had any suggestions I would recommend at least getting the 7.2 cubic foot freezer or larger, if you have room for it. I can keep 4 kegs and my 10lb co2 bottle inside the keezer with the 6 inch collar I built for it. If it were any smaller the bottle would have to come out and I wouldn't be able to put but two carboys in there.
I also would like to get a separate spare fridge to ferment in when my keezer has beer in it but that is several pages down on my list of things to do.
Kegged: BCS American Pale Ale, Blonde Ale
Primary: BCS American Pale Ale
Bottled: Janet's Brown Ale, Dry Stout, Irish Red Ale, Apfelwein
Gone:American Pale Ale, Irish Red Ale, Dry Stout, West Coast Red
Long Gone: Too much