First, let me say that, as a hotel, this is a very well run, comfortable establishment. Bed is very comfortable, shower hot (mild water pressure though), towels fresh and full, room and hallways clean, staff super friendly and helpful. Hotel breakfast is what a hotel breakfast should be - something for everyone with lots of fresh options (I give this very high marks).
So why three stars? This: I stayed here because some corporate training was nearby (ECTC). VERY convenient. But if you're not here for that, or to catch a flight to the airport, or for business near Dulles, you are out of the way. There is little in walking distance and what you can reach by car is ho hum. So if you are staying here as a tourist, I would not. Stay in the city or near a metro.
Bottom line - a GREAT hotel for corporate travelers.