Coulda been five stars, if ...
This one is a goodie with top-flight service, comfortable rooms, and a great location. So let's get the 'but' out of the way ....
But how in the world, in this day and age, can a place charge $12.95 a day for wireless?! Let that one sink in. The place is modern, full of comfort, great staff and THAT. Stop it, Marriott, please. That's flat gouging.
But the staff makes the place. Very helpful, always ready with a warm greeting, and there to make sure your stay is comfortable. Well done, staff.
The rooms are standard Marriott fare, so certainly no complaints there. The gym is decent, not great, and I never did make it to the pool. 
Metro stations are within walking distance, and there are plenty of restaurants, stores, Starbucks, etc. about. 
So get rid of the wireless fee and you are No. 1, Washington Marriott. Do that, I will return over and over again.