The Henry Hathaway classic is a movie i love. The story, action, scenery and characters are all well written. John Wayne gets his due as he plays a decidedly non-John Wayne character, Rooster Cogburn, perfectly. He won an Academy Award for his performance. He's charismatic, boisterous, funny, sad, and you are rooting for him in the climax battle. Jeff Corey and Robert Duvall make excellent antagonists, easily despicable. Glen Campbell is along for the ride, not much of an actor, but good enough to play off John Wayne. Strother Martin is also good, less scrungy than characters he's played, and funny. The only blemish on this movie is Kim Darby. She is dreadful. I have read a list of the other young women that could have had this role, and any of them (Tuesday Weld, Mia Farrow, Sally Field, Aissa Wayne, and Olivia Hussey) would have been better than Darby. She doesn't look right, and her acting is dreadful. That said, it's not enough to detract from an otherwise classic.
