Ebert, Roger (1975). One Flew Over the Cuckoo's Nest. Retrieved April 11, 2008, from rogerebert.com Web site: http://rogerebert.suntimes.com/apps/pbcs.dll/article?AID=/19750101/REVIEWS/501010348/1023

In his 1975 film review of One Flew Over the Cuckoo's Nest, Roger Ebert lauds the film for possessing stretches of brilliance, but states that the factor which keeps the movie from being great is director Forman's insistence on trying to assign to it a broader philosophical meaning. According to Ebert, the film attempts to be more significant than its story will allow. For example, in the scene in which Billy is discovered sharing a bed with one of the women McMurphy brought to the ward, Billy talks back to Nurse Ratched, his usual stutter conspicuously missing from his voice. The intention of this message is clear: it is devised to show that Billy has been liberated to some degree by both McMurphy and his nighttime experience. However, it lacks subtlety, and takes away from the film's generally thoughtful and three-dimensional characterizations. In fact, according to Ebert, it is these characterizations that constitute the best aspects of the film. Ebert believes that Forman should have focused his efforts on examining the characters and using their interactions to develop the film, rather than trying to create an antiestablishment parable.
I agree with the review on many of its key points. The movie's strongest facet is its ability to develop its characters and portray them in a way that demonstrates their change and growth throughout the story. McMurphy's significance as a character does not lie in his crusade against the establishment; rather, it is his ability as an individual to change the patients around him, and, by interacting with them in his carefree, individualistic manner, to release them of their inhibitions. It is also interesting how each character responds differently to McMurphy based on their personality. Cheswick, easily influenced, immediately takes to him, while Harding, who is naturally suspicious and guarded, never warms up to him. The nervous Billy is cautious but open, while the wild Taber does not seem to care about McMurphy's presence at all.