Having a positive view of Michael Mann's previous films, I'm tempted not to dwell on what stuck in my craw about Public Enemies. The film intermittently reaches dizzying heights of tone, tension, performance and presentation, but not often enough and never all at the same time. Great sequences like John Dillinger's escape from an Indiana jail have the magic combination of suspense and assuredness of staging, but are marred by other, more lackadaisical portions where the outcome feels like a foregone conclusion and there's no surprise in the execution.
The lengthy love story between Johnny Depp's Dillinger and Marion Cotillard's Billie Frechette feels unnecessary, though not especially tedious. Depp and Cotillard's scenes together feel more like an intrusion because there's nothing more to learn about Dillinger than when he is planning and executing his bank robberies. More interesting is Christian Bale's g-man, Melvin Purvis---it's a performance that illuminates what happens to Purvis after Mann's story ends (I won't spoil it), making you double back and reevaluate what Bale and Mann showed on screen.
The usual treats contained in Mann's films are there: detail-oriented production design, supporting cast of "Hey, it's that guy!" actors, and revelling in Mann's ambition for his film makes the sit worth it. The overall storytelling momentum isn't there, but the scope is worthy of respect.