We stayed about a week in DC for sightseeing. The apartment was ideally located for us, being a block away from the Colombia Heights Metro and 5 stops away from the Mall.
The apartment was well equipped, really comfortable and quiet at night. Colombia Heights is a pretty safe lively area with a good choice of places to eat - especially Pete's Pizza and the Heights restaurant.
We'd definitely recommend this apartment if you are coming to see the sights of Washington.