Pros: Elmar & Michelle are very kind, flexible, and responsive hosts. We did not meet them in person but had very good and helpful interactions through the app. They helped us with early check-in/late check-out and the place was exactly what we needed. Also, there is a lot of green in the patio, so it doesn't feel like you're in the middle of downtown DC.
Cons: If you're the type of traveler for whom decor matters, this place may not be for you. It has more of a 'rummage sale' / 'what was available' vibe than you might anticipate of an urban carriage house. Some quirks impact functionality (plates aren't microwaveable, certain features are at odd heights), but not in a major way.
For us, none of these things outweighed the value or location, but just know what you're getting to know if it aligns with your personal needs as a traveler.