While admittedly part of a small chain of brewpubs of the same name, I still prefer John Harvard's (1299 Pennsylvania Ave--at 13th St. NW about three blocks ENE of the Washington Monument). Corner entrance and downstairs. First impression might be that they're a little snobby, however, the bartenders I've encountered there are great and I'm a big fan of their IPA. But do sit at the bar.
Oh, for the uninitiated, Pennsylvania Ave can be a little confusing in that block. In short, if you're at the corner of 13th and Pennsylvania and you don't see John Harvard's on the northeast corner of the intersection, go down the hill one block (south) and try again because you're really at E St.
Dave