At Frugal Farmhouse Design, 1/4¨ plywood was cut down, painted/varnished and then glued/nailed over an existing subfloor.
It´s a traditional colonial/New England look that works well in this space, and seems to hold up well. Painted floors offer a range of interesting effects.
For a more modern look, these people took the ply up the wall and built a couple of bedside tables. I´m skeptical of their decision to put down the plywood over the carpeting.
Another good looking result at Quarry Orchard.
And, if and when we had the money and materials to upgrade, the ply planks serve as a subfloor.