I saw it this afternoon. I don't think it's anywhere near Heat or Collateral, or his "serious" movies like The Insider or Ali (which was better in its director's cut). But I'm still making up my mind about it. My friend and I talked about it for hours afterward, which is more than I can say for most other movies this summer.
Points of discussion:
+ cinematography. It looks like Collateral, for better or worse--personally, I liked the look of Collateral. The Universal logo is even washed out to match the movie's color palette.
+ when someone gets shot in that movie, you can be damn sure they're dead.
+ the muddy sound mix and the resultant garbled dialogue. Actually, that's a result of sound mix, plus assumed accents of actors, plus Michael Mann-speak. The characters often seem to be speaking some sort of invented cop language that reminded me of A Clockwork Orange more than anything else. I don't think I've heard the term "go-fast boat" used in any other film, and I'm not sure that that term describes anything that the word "speedboat" doesn't.
+ the troubling lack of character development, which is unlike a Michael Mann movie. There were no characters here that were as compelling for me as even the minor characters in Heat--they all seemed like ciphers, or types that were better executed in other Mann movies (the cop who juggles romance and his job, e.g.)
+ too much Farrell IMO; not enough Foxx.
+ a lot of loose ends in the plot--threads start up and get dropped with abandon. Characters live and die and you never find out their names. One gets the feeling that what plot there is was only nailed down in the editing room. When it works, the movie feels like a dream; when it doesn't, the movie feels half-assed.
I want to see it again to decide, and I really think it might benefit from a recut (like Ali did), but right now it feels like 2.5 stars/4 to me.