Good Conference Hotel, but Avoid the "Historic" Wardman Tower Section!
I stayed two nights. The first night was spent in the "historic" Wardman Tower, or "smelly" section of the hotel. The common areas had a mildewed air, the elevator smelled bad, and the room wasn't very fresh either. I planned to tough it out and not complain, but when I walked into the bathroom and stepped in water that had leaked from the base of the toilet, I asked for a different room. The good news is that the front desk responded right away with a really nice room in the modern section. I was paying a conference rate, so the second night was a great deal. The hotel offered 10,000 Marriott points for the inconvenience.
Note that the Wardman Tower is a long walk from the meeting rooms and other hotel amenities. It's interesting to walk through unless you're seriously allergic to anything. I don't know how they allocate the rooms, but you should avoid staying in this section if you can.
The location, right next to a Metro in a leafy part of town, is excellent.