Your coop looks fine! I built with OSB board too, and we had a rain and warped it and delaminated it. I was really disappointed in the way it did not hold up. Plywood will do a lot better being unprotected. Anyway, I ended up having to unscrew a couple of pieces and replace them since they would not lay flat again. I'd definitely paint it soon.
But otherwise, looks like a nice large area that will give you happy chickens!