The quality aspect is just something I've played around with in my head. I have never cared about the quality of the wood I burn. If it burns clean, its good, and the more the better.
Yet I live in an area that has an EXCESS of wood scraps. A great deal is cut off in dimensional lumber and other building supplies. I don't burn any thing, or take anything that is treated, and nails are not a problem. I take the ashes, and nails to the dump with the rest of dump stuff.
Its basically free heat, aside from the labor of locating it, loading it, unloading it and cutting it down to what the wood stove will handle. Of which I have become very lazy about the stove, as will take 17 inch bits.
The stove I have, is not a very efficient stove. Its a Olympic Avalon, and burns too hot all the time, even with the restrictions all closed, it still burns too fast for an over night stove. It has a fan and an exchange unit. I just chimmy sweeped it, after 15 years, and nothing was there to sweep out. I have cleaned the exchange coil several times, but it has to be a big blaze in this thing to heat up the house. It will take care of the power out situations, even with out the fan.
Being a bit of a nerd, it is far cheaper for me, and less labor to see the free fire wood sign and pay attention.
I'll stock up on any free wood, even bits left on the road. Of us, wood is always free.
I burn more in my burn piles, pulling stuff out of the woods for fire control, then I do finding easier stuff to put in the wood stove.