I recently had the pleasure of listening to L.A. Times film critic Kenneth Turan speak with Michael Mann, along with actors Tom Cruise and Barry Shabaka Henley, about Mann and company's new film COLLATERAL, 
and about the general representation of Los Angeles in film. As HEAT is one of my favorite films of all time and played an inordinately large part in drawing me to Los Angeles, the chance to listen to Mann talk about Los Angeles and film was basically a big ol' wet dream for me. The fact that they would also be showing extended clips of COLLATERAL was icing on the cake.
Michael Mann is the most visually exciting director currently working in American film. The way he composes a scene, his use of color and lighting, and the way he moves the camera combine to create films that are, on an aesthetic level, unbeatable. Naysayers are invited to revisit THE INSIDER, a film with a particularly uncinematic central character (with Russell Crowe in his best performance to date as an overweight, bispectacled scientist) and a visually uninspiring subject matter (a legal trial against tobacco companies), that through Mann's skill is transformed into cinema as exciting and kinetic as the best action film.
Note here, when I say "kinetic," I don't mean he moves the camera around a lot. Mann's camera movements, swooping helicopter shots aside, are largely noticeable; the camera moves to keep a moving subject in view (though not necessarily in focus). 
This goes directly in the face of the current rule of filmmaking that to create an exciting, dramatic moment, you've got to move the camera like it's strapped to a spastic grip who just pounded a heavily caffeinated beverage and is in the process of being electrocuted, even if (or especially if) the subject of the scene is doing something static like talking on a telephone. Jerking the camera around like it's on a bungee cord does not create excitement; it creates disorientation, which is nowhere near the same thing. It can work in an overwhelming, disorienting situation, like the storming of Omaha Beach in the opening of SAVING PRIVATE RYAN; it fails miserably in a godawful mess like PHONE BOOTH.
Merriam-Webster Online's definition of "kinetic":
1 : of or relating to the motion of material bodies and the forces and energy associated therewith
2 a : ACTIVE, LIVELY
2 b : DYNAMIC, ENERGIZING
That's what I mean when I say "kinetic." Or, to put it more simply, Michael Mann could film your grandmother taking a dump and make it look cool.
And while THE INSIDER is probably Mann's best film to date (ALI, the best film nobody saw in 2001, is darn close, and makes a great fist-pumping double feature when paired with WHEN WE WERE KINGS on a Saturday night), HEAT is hands down, his coolest. Not only is it visually perfect, but it's the best L.A. film since CHINATOWN; with it, Mann captures the bizarre aesthetic of this city better than any director before or since. It took eight years, with the making of the remake of THE ITALIAN JOB, of all things, before anyone else realized how cool something as uncool the Los Angeles subway system could look on film, but Mann had already got it with HEAT's opening scene. 
Other directors, jetting off to foreign lands for visually enticing climes, completely overlooked the wonderlands in their own backyards, while Mann, with HEAT (and later with the criminally underwatched television show ROBBERY HOMICIDE DIVISION), captured the seedy nightclubs, the sulfur mines, the tarp-shrouded chop shops, and the endless constellation of fallen stars that is Los Angeles at night, viewed from the hills. The legendary confrontation between Robert Deniro and Al Pacino's characters took place at a Bob's Big Boy in Burbank, for Pete's sake. The man knows L.A., and he knows how to make it look good, while not making it look like something else. He sees the beauty in what is largely considered to be an incredibly ugly city.
And from what I've seen of COLLATERAL, he's found even more. Shot largely in digital, Mann used a camera that, according to his description, is basically the size of a 35mm film camera attached to a good-sized refrigerator, to capture that particular Los Angeles twilight that starts when the sun sets and ends when it comes back up again, caused by the lights of the city reflecting off the cloud layer. COLLATERAL, the story of a Angelino cab driver (Jamie Foxx) who picks up the wrong fare in the form of a hitman named Vincent (played by Tom Cruise, in his second "Vince" role), takes place completely at night, and largely outdoors, which encouraged Mann to resort to digital film, not because he wanted to be able to manipulate the footage to include a couple million Stormtroopers or trolls, but because he wanted to fully capture what I a couple million others see out our car windows at night on the drive home. See, there's not enough ambient light for conventional film to capture anything in the Los Angeles pseudo-night without resorting to some major lighting help, as in the massive Kleig lights you see when you're going past a film set; but under that much light, you completely wash out the cool visual glow that you're trying to capture. So Mann went with the digital camera umbilicalled to the Frigidare, and ended up with, from what I saw, some amazing-looking footage. Which he's compiled, as far as I can tell, into an amazing-looking film. Which I'll have to wait until August to see.
In the meantime, I'm going to go watch HEAT again, and enjoy the view outside my window.