I stayed for a longer visit to DC and the place was fantastic. Mark is a great host, very welcoming, quick to respond, and provide advice on sites, food, and getting around DC. The apartment is comfortable and clean, and has a great kitchen if you plan to make some meals. The location is also quite nice - historic neighourhood, close to a metro stop, 10min walk to some good restaurants, and walking distance to the National Mall. I recommend staying here!