This film breaks my heart. Every time.
It's difficult to watch, like so many other great films, with long visual shots and little dialogue. The soundtrack, music by Ennio Morricone and other sound effects, still comprises most of the story - no surprise once you realize that a harmonica plays a key role from beginning to climax.
If you watch westerns you'll recognize most of the actors with speaking rolls, but traditionally the one that shocked America was beautiful Henry Fonda (blue eyes and all) as the sadistic and thoroughly hatable baddie. The romantic hero is played by Charles Bronson, as a native American. Another significant post-Colonialist move was placing a female at the center of the story, around which the plot moved, and through which, like the railroad, all parts met (an idea expressed in the amazing commentary (though John Carpenter comes off as kind of mean)).
A must-see. Ten out of ten. Right after Sergio Leone's other masterpiece: My Name is Nobody.