I mentioned the other day that the first "grown up" movie I ever was taken to was this one, "The Spy Who Loved Me." This was Roger Moore's third outing as "James Bond" (following "Live and Let Die" and "The Man With The Golden Gun"), and historically, by the time an actor has his third trip as 007, he REALLY hits his stride with his interpretation of the character. See Sean Connery's "Goldfinger" and Daniel Craig's "Skyfall" for proof of this theory.
Anyway, there's no question that Roger Moore's more self-deprecating, one-liner cracking, Bond was fully entrenched here. Also, this movie is known for three LEGENDARY things in the lore of the series:
1. The opening sequence sky diving stunt into an enormous chasm with Union Jack parachute
2. The Lotus Esprit Turbo (see above photo) that turns into a submarine
3. The villainous henchman, "Jaws" played by Richard Kiel (who was so popular they found a way to write him into the next story in the saga)
Also, and this is a debate for another time, but in my opinion, the greatest James Bond theme song ever from Carly Simon, the Oscar-nominated "Nobody Does It Better" (it lost to Debbie Boone's "You Light Up My Life")
"The Spy Who Love Me" is regarded by Roger Moore as his best Bond film, and financially was easily one of his most successful in the series. Interesting, in the closing credits it is revealed that "James Bond Will Return in For Your Eyes Only." However, after the runaway hysteria created by "Star Wars," this idea was shelved in favor of the space-themed, "Moonraker."
Opening in July of 1977, "The Spy Who Loved Me" was among the top 10 grossing films of the year.