A.O. Scott (The New York Times) calls it "One of the most remarkable experiments in the history of cinema." Roger Ebert says it "is on my list of the ten greatest films of all time." The film is 49 UP, and it airs tonight on PBS.
The film is the seventh film in a long-running series of documentaries that has traced the lives of 14 Brits, starting when they were 7 years old in 1964. The director, Michael Apted, has revisited these children every seven years (they are now 49 years old), watching how their lives have changed over the years. Talk about ambitious. You can watch a trailer for the film here, and listen to an interview with the director here.
P.S. The quote in the title comes from Salon.