Awesome location! We have often stayed further west (closer to Dupont) and walked to the buzz on 14th, so it was great fun to stay this close to it. We went to old favorites (Le Diplomate, Barcelona, Estadio, etc) and some new ones (Seven Reasons), and particularly enjoyed the coffee from next door at Bluestone Lane, which we got every morning. Reasonably close to the Green Line, but we tended to walk everywhere. Nearby TJs was great for stocking some cold drinks (heat wave was on when we arrived).
As I believe others have written, if the concierge is not at the desk when you arrive for check-in, you just have to wait. We waited about half an hour, but the Black Swan folks were very responsive by text, assuring us that someone would appear.
The apartment layout is efficient and has everything a traveler needs (except for a drying rack). We didn’t really use the kitchen but it’s fully equipped. The bed is comfortable and it’s quiet at night (we faced the back - no idea if it’s different for front-facing apartments). We would definitely recommend and return.