First, the communication with John, Justin, and Zach is incredible! They're extremely responsive and ready to answer any questions you may have.
The space of both places was fantastic for our group of 10. The apartment downstairs was great for the people that wanted to stay out a little later than the rest of the group while the upstairs was big enough to have everyone gathered for dinner and games.
It's not walkable distance to most of the attractions in DC. The metro is about a half mile which isn't bad for adults, but if you have kids under 10, it starts to feel pretty far away. So, just make sure you plan for that if that's the case for your group.
Overall, it was a very nice stay and my entire group had a great time! You must try Call Your Mother which is right at the end of the street, great breakfast sandwiches!