It's just plain thrilling. Each star truly makes the agony of their character's dilemmas believable and the difficulties of survival in the pre-modern West very real. Pride, hatred, love, and respect are the keywords here and they are writ large against a magnificent panorama of real and personal canyons. It does not accomplish this didactically, but compellingly through the dignity and suffering of its characters. He clearly has fallen in love with Ellen Grange, but his decency constrains him and the movie's grace is that it doesn't not capitalize on their possible relationship, nor bother with big issues of honor.
Survival is almost all.
The beauty of the film is that it is all about action, but in the end what lingers are its values, which are darn good. The cinematography by Charles Wheeler is fabulous, almost as great, stirring and memorable as the score by Neal Hefti that ties together its various plots. It is one of the best in film history, not for originality but for its anthemic power. A relatively simple theme, it is persistent, uplifting, and of great moment. Poitier's important presence in the film is almost too politically correct, but shock quickly dissipates because of his competence.