A fine biopic of Johnny Cash, Walk the Line's only real problems are the same problems that assail all biopics. Let's start with the good:

Joaquin Phoenix is excellent, nailing Cash's singing voice and mannerisms as best he can. Reese Witherspoon does even better in a difficult role: she has to make June sympathetic, but not a doormat and succeeds. As typical in biopics, the performances of the leads dominate the film--other characters are only seen fleetingly and one must fill in their gaps themselves (trying to understand the point of view of such characters as Johnny's first wife and his mother, based on their screen time alone, is nearly impossible without making some suppositions). Robert Patrick, an excellent actor, has the undemanding role of Johnny's unloving father, another biopic staple (Patrick played Elvis' dad in a TV miniseries--what's next, Dad Orbison?).

The film also benefits from a nice, straightforward telling. There's some melodrama as expected, but nobody has a Big Oscar Monologue, pop psychology is kept to a minimum (so no ghostly Cash older brother), and the few melodramatic scenes can be forgiven (Johnny going crazy at home, the pretty soppy final scene).

Other problems may be more personal. The Folsom Prison scene should be a capper, but its relative brevity dilutes its impact. The fact that most of the film takes place as a series of flashbacks (a cheesy conceit) sets this scene up as important when it almost comes off as just another check in the Cash Checklist.

The biggest flaw the film has is the scattershot nature that biopics have. Jon Stewart joked that Walk the Line is Ray with white people and while that's not quite fair, a lot of the same cliches pop up. A difference I noted is that while Ray Charles did unlikeable things, he seemed likeable and we got the impression that if he was off drugs and wasn't being used, he would be fine. Johnny Cash, on the other hand, almost immediately becomes a real jerk once he hits stardom, and it's to Phoenix's credit that he can keep the audience's sympathy for the most part. It's hard to tell how much of it is the script and how much of it is the general feeling of rapid-fire scenes: there's not enough time to show a gradual descent, so the film just has Cash doing a swan dive into his personal demons.

The film has a lot of great Cash music, although it seems that the more signature Cash tunes are only heard fleetingly.