Positives: definably the location and great communication with the host. We found it so easy to walk to restaurants, Whole Foods, and the Mall.
The flat is in-between two others, so depending on how full the whole building is, you will hear the floor above you go past the door and walk upstairs. Using the water and heat turns on loud fans and heating sources. Not a major issue but not all that quiet either.
Cleanliness: There were several items of trash under both beds; no coffee filters that fit correctly for the coffee maker (and I sent a note and responded to the request for the coffee maker model, but never received correct ones); the living space badly needs a better couch/chairs as the ones that are there are really uncomfortable and don't lend themselves to a gathering space; one bedroom only had one night table and I think the other one got taken out into the living room; we all found it strange and unappealing that the silverware drawer was directly above the trash can and only could be found when we opened the trash drawer.
We enjoyed our stay in DC and were not in the apartment much because it really didn't lend itself to sitting around together, so instead, we just went out to a restaurant. If we returned, I'd likely look for another place knowing what we know now.