I have one single retired woman friend and two retired couples who moved to Ballston and love it. My thirtysomething daughter and her husband have lived in Ballston for a few years and bought a condo there last year. The do not need a car; she works two blocks from her employer and he commutes to Fairfax County via metro; both mostly work at home.
Ballston to Courthouse are very walkable, or a short metro ride apart. The residents are pretty young…even my thirtysomethings sometime feel old!
They love Arlington; DH and I live in Alexandria, and this is just right for both of us.