Not up to Mandarin Oriental standard - not a fan.....
Organised a quick weekend getaway from Zurich to Washington DC, primarily to try the new Lufthansa 747-8i and chose this hotel as we had stayed at a number of their other properties and had always been impressed.
We were met but a hotel driver who was imformative about the city. We were met at the door by one of the team and shown to the room. The hotel was booked through the Amex Fine Hotels and Resorts Program so as some of you may be aware there are certain inclusions. We did not receive our upgrade which is no disaster. I am a believer in if you want a certain room type then that is the one you should book. We had booked a Tai Pan Executive Harbour View. The gentleman checking us in then did offer us the Mandarin Suite (for an extra amount per night) or a suite fo no additional charge. 
We elected to take the Mandarin Suite which was probably a bit excessive but it was quite a nice room but the view was spectactular. You saw the Pentagon, Jefferson Memorial, the nearby water and Reagan Airport. The room, like the rest of the hotel, is getting a little bit dated and the furnishings and decor were showing this.There was a large lounge/dining area and powder room. The bedroom was a good size and had decent amenities but no different to a standard room.
The executive lounge was a reasonable size and you can get local beers, wines and soft drinks all day (I was surpised by this!) and then spirits in the evening with light snacks. Be aware that champagne is not included at any time (this is unusual). Breakfast did include some hot items and usual continental items. Coffee was typically American which was ok. Note that there a few staff in the lounge but we could not work out what they did. They certainly did not seem interested in looking after the guests! The highlight (well, it was a lowlight) for us in the lounge was one guest who decided to have breakfast in his bathrobe after a swim and was holding his swimming trunks in his hand....clearly nothing else was below the bathrobe, We mentioned this at checkout that a dress standard was not enforced....little reaction.
Also, if you are an Amex holder and have booked this was the credit you receive toward food and beverage is NOT able to be used at their premium restaurant CityZen. We only discovered this on checking in and it seems Amex is not aware of this. We still decided to eat there and the food and ambience is very good. Really extensive winelist also. We also ate (breakfast and dinner) at their other restaurant). The food is fine but the service is very average. Make sure you avoid any seats near the wine fridge as it is very noisy but they did kindly switch it off. For me the poor service was around delivering our main courses before we had finished our appetizers - who does that?
We also had some issues with very dodgy turn down service but the icing on the cake was a staff member walking into the room when the Do Not Disturb sign was on. He indicated that he knocked but it seems irrelevant to me if the light is on. 
On checkout we made the duty front desk manager aware of the issues and he was very silent on the matter and indicated that he would talk to his manager. We did hear back with an offer of a complementary night which, although kind, is of little value as we have no immediate plans to return to Washington.
To be honest, we will not be rushing back to this hotel even when we do go back.