We were three in the apartment and had a great stay. The location is quite good, great places to eat and drink exist nearby. A parking permit can be issued for an additional charge and the price is very fair. In the street you can actually always find a parking space.
Check-in and check-out were uncomplicated. The contact with the hosts was always very friendly. The apartment is well equipped and clean. In the living room, the usual entertainment program is available with an Internet-capable TV (appropriate own accounts required). There is a small selection of board games and books.
It is important for a travel group to know that the bedroom is a passage room to the bathroom. The apartment is indeed weak soundproofed as described, but the hosts have taken care to reduce the noise to the minimum.
Overall, the apartment can be fully recommended for a stay in Washington D.C.!