Greetings gang! It's been a while. I "finished" my under stair cellar (except for completing a few mostly aesthetic door details) last spring. I ended up using spray foam insulation and not insulating the floor at all. It held up well to a brutal Atlanta summer and I have been steadily filling it up.
For the door, I spent several months gluing corks to a custom cut piece of plywood, and just recently secured it to the inside of the cellar door. It worked out very nicely; looks great and adds a nominal R-value to the door.
I'll get some more pics on here. I think an understair cellar is a great option for folks with limited space and I couldn't be happier with it. This forum was a terrific resource as the project went on. Thanks to you all!