I have tried to watch it several times before, but could never get past that first scene with the balloon. Fritz Lang directed this 1931 movie. I always enjoy Peter Lorre.
Moria gives it 4 out of 5 stars. 1000 Misspent Hours provides some historical context:
Fritz Lang and Peter Lorre were both Jews, and Germany in 1931 was already nearly as bad a place to be Jewish as it would famously become a couple of years later. Worse yet, the owner of the studio where M was filmed was also a Nazi party activist! (That studio owner is the main reason for the film’s enigmatic title— when Lang came to him with a movie called Murders Among Us, the moneyman assumed he was being asked to produce an anti-Nazi political film, and refused to have anything to do with the project!) Though the subject never explicitly comes up, the early scenes depicting the terror-stricken townspeople scapegoating each other on the flimsiest of excuses, often threatening actual physical violence, take on a powerful subtext when you look at M as a product of its time and place.It's on Roger Ebert's "great movies" list. 1001Flicks has a review. Images Journal reviews it here. Bright Lights Film Journal calls it "masterful". Senses of Cinema says it's "perhaps [Lang's] greatest work". Criterion offers an edition of this film.
4/22/2008:FilmsNoir posts a link to a review.
9/1/2008:MovieZeal has a review.