For our needs it was nearly perfect, and we will stay here again if(when) we're in DC again. I thought I'd list some pros and cons so people can decide themselves.
Pros:
Plenty of room/space considering location.
Great high quality appliances/shower/etc.
Great transit access/location (bus stops on the same block/across the street, metro station a 15m walk or 7m bus ride).
Great communication with host and in-house amenities provided.
The AC definitely works - we visited during the hottest part of the year and it was a relief to come home and shower and not immediately start sweating again. There are plenty of blankets and heaters it if it gets to be too cold, and fans if you need a little more circulation.
I like the extra safety of a gate that locks as well as the door, but it is a little difficult to maneuver coming and going until you get used to the steep steps and gate.
Cons:
Bedroom/bed/window is right off the street, and this is a busy street at all hours. Not an issue for us because we live in a similar situation at home.
The street/neighborhood is mid-gentrification, just like DC as a whole. If the idea of riding the city bus or being near the "unwashed masses" bothers you, don't stay here. We ARE the unwashed masses so, again, no biggie.
Basement units mean low ceilings, upstairs neighbor noise, and bugs.
The bed is very, very soft and not super deep/tall. I, a large person, bottomed out the springs sitting on the edge. But it was comfortable to sleep in. The sheets are old and pilling; my husband found them scratchy.
The only windows are in the bedroom.
Check that you have what you need/want before you go shopping for groceries if you plan to cook; we didn't realize there wasn't a cookie pan until we were getting ready to start cooking. We made it work without but definitely investigate.
Don't expect it to be clean enough to eat off the baseboards; it's very much the average level of cleanliness that you'd expect from somewhere without a permanent full time resident.