Today I finished the next coat of mud, showed the addition and kitchen remodel to a long-time friend from Habitat, and actually got the 1/4" plywood to smooth out the subfloor.
The plywood is so smooth and lovely that we're considering using it as the flooring. I just need to find a durable enough (and non-toxic) finish to protect it, and a good way to fasten it down. I'm contemplating ripping it into 2x8 or maybe 1x8 strips, so it can be laid out in a staggered pattern. In any event, we'll have it as our flooring for a while to consider, so we can see if we like the look or not.
The plywood is so smooth that I had a hard time securing it to the roof. It seemed OK, but it slid significantly when I braked. While I was stopped to refasten the load, someone stopped and asked me for directions that I could actually give (and had a map to show them), so it worked out nicely.