It's probably impossible to make one of these bio films and have the final product not feel a little bit formulaic- not only do the films generally follow the typical 3-act story arc, but every scene has to be a vital moment in the person's life. The final result is that you see a singer sitting around and writing his songs, or a politician practicing his speeches in front of a mirror, but not a lot of those moments in their life that weren't vital. We don't get a feeling for who the person was so much as what big things they did.
Walk the Line has the same problem in this respect. When we see Johnny Cash glance at a boy shining shoes while he walks down the street, there's no wonder that he will sing about a shoe shine boy a few scenes later. When June Carter tells him that he had better get sobered up and "walk the line", we know exactly what's coming next... Not only does the film feel formulaic, but it feels like the writers and filmmakers didn't try very hard to get past the limitations of the genre.
Which is a shame because Reece Witherspoon, that human transliteration of a Betty Boop cartoon, is fantastic here as June Carter Cash, and the original Johnny Cash songs are as heartfelt and genuine as ever. In fact, there's a disconnect between the filmmaking, which feels rushed and mechanical, and the music, which burns like a shot of Jack Daniel's whiskey going down... still.
Johnny Cash deserved something better than this. Juaqin Phoenix has his stance and stare down, but mistakes stumbling and mumbling for acting. The worst sin; he's boring. Walk the Line isn't terrible by any stretch of the imagination, but it's tepid. Cash's intensely-felt Christianity has been largely left out, and his parents have been made into one-note stock "Southern" characters- the father is drunk and abusive and mom won't stop singing hymnals! Instead, the focus is on his drug abuse, which was important, but one gets the feeling that this was the only aspect of the story that the filmmakers had any genuine feeling for. Drug movies follow the same 'redemption' storyline that, in this case, further mechanizes things. Every little thing in Act 1 pushes the main character to the drug abuse in Act 2, which is finally resolved in Act 3. This is movie-of-the-week stuff.