We stayed at the Mandarin in DC two summers ago. We had two rooms on the Tai Pan level(concierge level). The rooms are very nice, bathrooms are beautiful and I remember the beds being very comfy(nice bedding). If you're staying on this level, definitely take advantage of the breakfast and afternoon snacks and drinks.
The hotel is beautiful but my family felt a little out of place. My kids are used to family friendly places...and this is definitely upscale. We didn't use the pool at all...just no time to. The onsite restaurants are very expensive. There aren't many nearby restaurants...at least there weren't two years ago. There is a Starbucks and a Potbelly.
Other than the lack of food nearby, the location is wonderful. Great views of the city. Don't worry about noise. We had a car and they have onsite parking...which is expensive. We used our car to find dinner but certainly didn't need it for touring.