I'd wanted to see this in the cinema, but unfortunately I was far from mobile at the time (recovering from an operation), so I finally got to see it the other day. I was quite excited about it initially, being that it's the new Michael Mann movie, and it simply looked a lot better than what Miami Vice had been.
That said, I am willing to give Miami Vice another go at some point, and even though I was far from impressed by it at the time, I still found it to be a beautiful looking film with the same sense of drama, colour and love of architecture that you always find in a Mann film.
Public Enemies though, really is a lot better than Miami Vice, so that's good news to start with. Unfortunately, it's still not as convincing as the likes of Manhunter, Heat, or Collateral. There's just a little bit of something missing. We don't have the strong underlying relationship between protagonist and antagonist like those three aforementioned films all exhibited (profoundly in the case of Heat).
Dillinger's relationship with his lady is mostly perfunctory, and his cat & mouse dealings with Purvis are few and not particularly meaty. Still, Depp is always compelling to watch, and Bale's Purvis is a strong, decent protagonist - even if he is somewhat sidelined in favour of the romanticised Depression era Robin Hood-like Dillinger.
Action wise though, similar to Heat, it's all guns blazing. Deafening cacophonies of gunfire erupt frequently throughout, and even though Mann has never done a gunfight better than the street battle outside the bank in Heat, Mann on less-than-tip-top form is far better than most.
At the best part of two and a half hours long though, the lack of meat between the main characters does lead the film to drag a bit. While Heat is a long film, the characters are so dense in personality and motivation that the length is required. In Public Enemies you start feeling a bit short-changed, never really getting to know any of the key players deep enough to really, really care about them.
This said, Mann has always had a knack for spine-chillingly tense and dramatic endings. Heat's Moby-scored ("God Moving Over The Waters") airport gun-down, Collateral's urban train ride at dawn, and even Miami Vice's Mogwai-scored ("Auto Rock") all stick out, and Public Enemies has a similar flair for the dramatic with a tense build-up to the inevitable. In Mann's world crime ultimately doesn't pay, but that's no excuse not to go out memorably.
So not his finest work, but he's put out worse, and like Mark Kermode said a few months back when the film first opened, even Michael Mann on a less-than-stellar day is better than most directors on a great day.