I disagree. I thought Faramir was portrayed quite well. It depends how you interpret his actions onscreen. I didn’t see his actions as one of ambition when he held the ring, but one of, “This is what people are after?”
Faramir initially tries to bring them back to Gondor in the movie, but in the book he doesn’t do that; he doesn’t want the ring, and helps them on their way. The distinction is important, as it shows that he (like Aragorn) still retain some of the purity of the men from long ago.