I often stay with my friend who lives in Rockville/North Bethesda, and what shmessy says has some real merit.
My impression of the walking section, near the Metro, of Bethesda is that it's basically a good place -- for a suburb. Kind of boring, upscale, gentrified. There's shops, restaurants, lots of families, etc. The Metro station entrance is in a strange spot, kind of a dull plaza, but maybe it's busier during working hours. I'd much rather be in D.C. itself, or any of those places you listed in Boston. So I guess I disagree with that part of his statement.
Rockville, at least where he lives, is a landscape of nasty highways, four-lane high speed "Lanes", empty greenspaces, big parking lots, strip malls, and big residential towers-in-the-park ... punctuated by the occasional Metro station, so at least you can get the hell outta there fast!