Compared to Sarah, I really enjoyed the movie. That said, I think that, while I may not agree with all of her points, many of her complaints are fair. Though it didn't strike me at the time, I think her characterization of Bale's character is accurate. The love story is as "meh" as you could expect (never Michael Mann's forte), and you don't walk out with any particularly strong emotional ties to any of the characters. The movie is also definitely as much about now as the 1930s, not just in terms of heavy-handed interrogation techniques, but also in terms of the economy (people celebrating Dillinger for attacking the banks that had gotten them in the mess isn't so far from people celebrating things like Madoff's arrest or anger at AGI). I also enjoy many Michael Mann films, and admitted as we left (when some who saw it with me were underwhelmed) that you know what you're getting with him generally, and you know whether you like it or not.
However, there are a couple of things I think that make it better than Sarah felt it was. First, the one acting job that really stuck out for me was Billy Crudup as J. Edgar Hoover. It wasn't just that he got the speech mannerisms dead on. I really felt that he did an excellent job in showing what a power-hungry and manipulative leader he was, and he did as much with his characterization through body language (particularly in the way he bristles when being accused before a Senate committee of having never arrested anybody) as he did when he spoke.
I also really liked the scenery - yes, it was period pieces, but the way Mann used the environment/lighting/framing to shift the mood of the film overall was excellentl. There's a constant sense of growing ambiguity/darkness as the film shifts from the the big, blue, sunny sky of the Indiana plains at the beginning, and then used those aforementioned elements to make the movie darker and darker as time passed. And the gun battles were amazingly choreographed and shot (no pun intended), marking Mann's best work since Heat. The battle at the lodge was particularly impressive, and was hands-down the best I've seen since the showdown at the end of L.A. Confidential.
The other thing that I think makes this a really notable movie is that it's the first live-action movie filmed digitally where I could actually see some of the potential for that method of filming. Previous digital movies (Benjamin Button, I'm looking at you) left me saying, "what's the big deal?" It's like directors haven't figured out what to do with it yet, or how to take advantage of the format. With Public Enemies, you finally start to get a sense of what digital formatting offers. The film had a clarity and beauty that other films lacked (though the prison against the open sky in the opening sequence is a fairly breath-taking shot). The night-time scenes were the best evidence of digital's potential, though, as Mann was able to make nighttime look more brilliant (without appearing falsely illuminated) than any movie I've ever seen. It wasn't so much a matter of camera angles or lighting tricks (though no doubt those entered into the equation some) - it was clear that the digital format just made for better filming for those scenes, and they have a beauty unlike any beforehand (though to be clear, that doesn't mean they are the most beautiful night-time scenes).
I suspect general opinions about the movie will come down to the differences that Sarah and I have over it. If you're looking for a great story, compelling characters, or a convincing love-story, you're going to be underwhelmed. If you enjoy Michael Mann movies for what they are (and if you don't, there's nothing wrong with you), and can appreciate the way in which somebody seems to finally be figuring out how to use the digital format for a more brilliant and beautiful film, then you will probably highly enjoy it.