This film pulls together three key elements of American mythology--the West, capitalism, and religion. It is an incredibly ambitious film, which doesn't operate by making statements about these elements, but juxtaposes them to provide the audience with a chance to ponder their relationship--that is, until the end, where an over-the-top, and overly simplified final scene brings the movie to an unsatisfying end.
But, up until the last 15 minutes, the film takes one's breath away. And it could not be so without Daniel Day-Lewis' fine portrayal of a misanthropic oil man. He is both hero (for holding out against the monopoly of Standard Oil) and villain (for his treatment of his son, and the townspeople). He is not wholly bad, but one realizes that his good deeds ultimately are in service of his greed, and, paradoxically, are a function of his hatred of others and his desire to ultimately be alone.
The other acting is good as well, especially Dillon Freasier in the role of Day-Lewis's son, H.W. I felt that Paul Dano was outmatched by Day-Lewis (who wouldn't be?). Whereas Day-Lewis played magnificently the juxtaposition of irony and sincerity in his "conversion" scene, I felt Dano tilted too much towards an ironic portrayal in his early scenes as an evangelical preacher. Yes, we do find out in the end that he was a charlatan, but, in order for him to gain a following, he would have had to come across as more charismatic in his preaching scenes. And there is the problem of his looking and acting the same as an older man in the problematic final scene.
The score was amazing. Many film scores just linger in the background, having more of an unconscious effect. This score constantly intruded, sometimes contradicting the action, sometimes reaching a climax before the filmed image did, which helps to heighten the uneasy feeling of danger one must have felt working on an oil rig at the time. The use of silence, especially in the opening scene, where we just observe Day-Lewis alone as a prospector, was very effective. The cinematography was beautiful, and the film was a pleasure to watch.