Ha and Justin's place for perfect for my work trip to DC.
The location is close to the metro and a couple of bus lines, as well as neighborhood restaurants (Mexican and Salvadorian in this particular neighborhood-- I also highly recommend Ababa Ethiopian on 18th street (a slightly longer walk, but worth it).
My favorite part: the apartment was just a few blocks from Rock Creek for morning and evening runs, and I walked through the zoo (via the back entrance) on my way to my conference. The apartment had everything you could need, including a rain poncho and an umbrella (not needed this trip, but the touch was appreciated).
Ha and Justin were also extremely attentive, keeping in touch both before and during my visit. I recommend their place highly and without reservation.