Peter Lorre has such a bizarre and creepy screen pressence. He is sort of like Steve Buscemi, if Steve Buscemi had a thick Austrian accent. And so when I heard that Fritz Lang's M cast Lorre as a pedophile I thought, "that is perfect casting." Not to say that I thought Peter Lorre was a pedophile, but I can't think of anyone who would be able to convincingly play one better. But here's the problem - a good deal of Peter Lorre's creepiness comes from his bizarre accent. M removes that level of creepiness - Lorre speaking German just doesn't sound nearly as disturbing as Lorre speaking English. That is not to say that I think Lorre is bad in the part - he is very good - but, at first, I was disappointed in his voice. I got over it, (the excellence of the film certainly helped with that), but still... I would have liked to see Peter Lorre as an English-speaking pedophile.
With that minor gripe out of the way, I can move on to what I thought of the movie as a whole. It was really good. This was Fritz Lang's first sound film, and he uses sound quite sparingly, but very effectively. Peter Lorre's whistling of In the Hall of the Mountain King is a startlingly effective leitmotif, forcing the audience to experience his presence, even when he is unseen. Lang's command of visuals is in full display as well - it is a rare film that has this many beautiful shots of grotesque people in extreme close up.
The pacing is maybe a little slow in places, but the atmosphere the film evokes is so powerful that the occassional slow spot hardly matters at all. Sometimes it actually works to help the film, by keeping you in suspence. There is an almost totally irrelevant fifteen minute sequence of some policemen trying to interrogate a petty criminal that takes place during the film's climax, and just works to whet the audience's appetite for what is to come. You sit there thinking, "hurry up! Get back to Peter Lorre!" but not in a bored way, in a mood of intense anticipation. Then when Lang finally does move on to the Lorre stuff, he doesn't disappoint, and all the waiting seems worthwhile.