Nice But Overpriced
I've stayed at the J.W. in Bangkok and absolutely loved it, but the one in Washington, DC was lacking in many ways. The service is good, but the rooms are smaller than I expected and there are very few perks. No complimentary anything. No breakfast, no free internet ($13/day), no evening drinks, etc. They even charged me $5 to receive a package there. 
I stayed here for a week and am glad I didn't bring the family along. Location is the primary perk to this hotel, being on Pennsylvania Ave., but I am just as happy to stay a few blocks away to get more bang for the buck. 
To their credit, I should have read the description much closer on the Marriott website and the gym is slightly better than average. However, next time I'm in DC, I'll stay at the Residence Inn Marriott off of Vermont Ave. or the Hilton.