Two years after my initial query....while I didn't manage to make the flight then, I did fly Southern Airways Express from Bradford, PA (BFD) to Dulles today.

Small Cessna, 4 pax. As above, no lav and a nice, clean, very new-looking airport experience in BFD. Had to wait on the tarmac for 5 min or so for a passenger van to get us to the terminal at Dulles.

Ridiculously cheap fare, $69 one way with 2 day advance purchase.