Verdict:

The starting credits show the characters as they appear in scenes from the movie. That is something you would see at the start of a long-running show, but it looks weird in a movie. It’s like a collage of almost spoilers. Anyway…
Parts of this movie can be hard to understand and that is largely due to how characters speak. For one, a number of them, especially the main villain, speak with an accent that takes a moment to decipher. But the movie moves too fast for you to do that. Then there is the fact that they use fancy gangster language, like “fold the con” and contemporary terms like “Faro” (a card game, apparently). A combination of this cool language, accents and quick mumbled speech means that it is hard to understand anyone. Sometimes every sentence in a scene is affected. Some dialogue occurs too far in the background and some of it does not get enough set-up. Maybe this makes the movie sound realistic and smart, but it also results in loss of meaning.
Where the movie really shines is when it comes to its performances. The two main leads, Robert Redford and Paul Newman are charming as hell. They are the archetypes of charming bandits. The comedic timing is impeccable, and the dialogue can be very witty (when understandable).
It’s unfortunate that the villain, played by Robert Shaw, comes off as such a weak character. He looks intelligent, but he eats up everything the other con artists feed him.
The cinematography is so good and the performances are so good that the film successfully creates an illusion of being very cool and witty. Everyone in it appears cool and witty, while the ragtime music underlines the convoluted fast-paced action.
But the story will break down if you think too much about it. For example, without spoiling too much, ask yourself after watching this movie: why would a trained assassin waste several days pretending to be someone else just to kill an unarmed person when there were countless opportunities to do so already, and the answer is clear: for the sake of an exciting twist. Another example: the two main characters are shown to be down on their luck, and the con they come up with involves an army of people, rented spaces and other investments. So how did they finance their big job exactly? Don’t ask.
It feels like this movie conned audiences into believing that was smarter than it is and it conned The Academy of Motion Picture Arts and Sciences into giving it 7 Oscars, which seems absolutely baffling given the shaky plot, messy speech and the weak villain. Having said that, it is still really charming and well-acted, no doubt about it.