The movie seemed entirely too focused on how good Johnny Depp looks in deep close-up, and failed to focus on the far more interesting character of Melvin Purvis (Christian Bale) and the investigation and pursuit of Dillinger. Mann makes a weak attempt to emulate (steal from) The Wire by showing us quick glimpses of the FBI's investigative process (even going so far as to cast two actors from that vastly superior show), but never fully explores this aspect of the story, choosing to pay far too brief lip-service to the detective work and the building of Purvis' task force.
Yes, the action scenes are good; Mann has always been skilled at crafting such sequences. But they are few and far between, and the between consists of watching Depp swipe away stray locks of hair from his forehead, albeit quite charismatically, and gazing meaningfully at his fellow actors. I kept waiting for "In the Air Tonight" to start playing in the background.
The movie tries to paint a detailed portrait of Dillinger in this manner, but ultimately his motivations boil down to "live life to the fullest," which is very nice for a fortune cookie, but pretty much a death sentence for a 2 1/3 hour movie. Carpe diem, we get it.
The cinematography, while very picturesque, is on the whole overly conventional, which is very disappointing considering Mann's past visual work. I suppose the argument could be made that it was purposefully understated, but there's nothing to counterpoint it through most of the movie, so it becomes ultimately ineffective. And by ineffective I mean DULL.
Basically, Brian DePalma showed us how it's done over 20 years ago, and filmmakers just keep failing to look at the damn template.