I don't need to summarize this movie as other reviewers have already done a good job at it. I was a bit disappointed with the movie because of all the hype I had heard from critics and from peers. I found the story to be not all that compelling and even the characters are not that captivating. The only character with any depth is the main character and his story his pretty simple - he's alone and poor, he's ambitious, he's successful, he's miserable, he goes crazy. Citizen Kane anyone?
All in all, after speaking with friends about this movie, I have found that many people like the message "greed + ambition = evil" more than the movie itself. However, this message is only part of the movie because it would be just as easy to view the opposite message that all the honest people eventually end up getting the raw end of the deal "honesty = foolishness"?. Everyone appears to be miserable in this movie with no consistent message as everyone seems to be just as miserable before industrialization than after.
In the end, after the movie was over, I wasn't moved, intrigued, or impressed. My first thoughts were "great acting by Daniel Day-Lewis, cool soundtrack, nice landscapes and dark imagery, and interesting vignettes of the zeitgeist of the early 20th century oil craze (hopefully it is somewhat accurate)".
In summary, I can find intellectual reasons why this movie is good. However, it didn't stir up any intense feelings nor did it send me on a long thinking binge. Consequently, I can say that this movie is "good" and "worth seeing", but I can't say that it is "great" and a "must see".