We loved staying at Mark's place! He has great tastes and it shows in the decor and design. Everything was clean and seemed new. We were welcomed with all the conveniences needed. Wife and I slept on a firm comfortable bed, kids got a pull-out sofa bed in a separate living room, there were televisions in each room with cable and wifi internet access plus a powerful waterfall showerhead in the bathroom. Kitchen came in one night as well as we decided to eat in (Trader Joe's is just 5min walk away) and the included washer/dryer meant we got to go home with a suitcase of clean clothes.
Mark's place is located in a great spot in Foggy Bottom, 10-15 minute walk from crowded Georgetown shopping area and the waterfront on one side and a 20 minute walk to other great areas of DC (such as Dupont Circle) and monuments (such as Lincoln Memorial). There are rental bikes on the corner which make it easy and expensive to get around and take in the sights.
Would definitely recommend, we hope to return in a couple years and will checkout Mark's place again!