She remains the first really successful commercial jet, and still defines our concept of what constitutes a modern airliner, in terms of appearance, general layout, speed, and passenger arrangement/amenities.
Things she introduced to airliners that are still in use on them: landing-gear trucks, leading-edge flaps, aereolastic wing design, podded engines, and fail-safe fatigue design.
Other than decorating/style details, sitting in a 707 today, a passenger would be hard-pressed to know what aircraft type they were riding in.
She lives on with her fuselage sections being fundamentally the same as those used in the 727, 737, and 757, and her nose and cockpit will continue as the same cramped and noisy place in the 737 (sans eyebrow windows) as first flew in July, 1954 (thanks SWA).
