I second the Bethesda North Marriott as a good option. It is literally across the street from the Red Line stop. As mentioned, right now for DC, it is ESSENTIAL to make sure you know the Metro track work schedule (currently available here: http://www.wmata.com/rail/safetrack.cfm). If the red line is where you need to be, and there is no track work on that line, Bethesda North is a great choice if you are okay with a 25 minutes easy subway ride into downtown. As noted, concierge lounge is among the better ones IMO.

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Additional info: Sorry, I see others already posted the SafeTrack link! Doesn't hurt to repeat it I supposed given how important it is to DC travel this coming year. Also, I'd note that Bethesda North is a Category 4, in case you're using points (i.e., not a Cat 5), versus using one of the Category 1-5 certs. Even if you are using a cert, because my travel takes me to the Union Station area (i.e., on the Red Line), Bethesda North is my choice. (I frequently stay in DC for work/leisure travel.)