Our stay in Katie and Matthias' flat was outstanding. Katie and Matthias are great hosts, very thoughtful (the place was spotless, with a bottle of wine waiting for us on arrival and when we encountered issues with the door, they were super quick to reply and help us out).
Their flat is so stylish and in a great location, making it very easy to venture out and explore DC, especially as they had left us great recommendations and metro cards if needed.
I would recommend their airbnb if you're in DC and looking for a home away from home for a couple of days!