The film is eeriely authentic to the story arcs it's taken from the comic book. Not just in plot and dialogue, but in style, camera angle, and chosen shots. The filmmakers essentially used the comic book as a storyboard. It's an extraordinarily faithful adaptation. The technical achievement in doing that, alone, is impressive. (Here's a frame-by-frame comparison based on some of the trailers and early footage released, and that'll give you an idea of just how faithful it is. Also chock-full of spoilers, so I don't recommend it if you've neither seen the movie or the comic book. And NOT WORK SAFE.)
That said, it's a faithful adaptation of a sex-and-violence-laden, film-noir-style comic book. If you like movies like "Pulp Fiction", you should enjoy this film. (Lut suggests "Kill Bill" would be a better comparison, and that "Pulp Fiction" is less violent than "Sin City". I haven't seen "Kill Bill", myself.) But this is definitely not a film that everyone would enjoy. I have a reasonably high tolerance for violence, but some of the scenes made me nauseous; one of them even turned Lut's stomach a bit.
Some of the actors do a great job of capturing their characters. Mickey Rourke's Marv feels right, as does Bruce Willis's Hartigan. Jessica Alba didn't quite cut it for me as Nancy Callahan, though. In fact, even the little-girl Nancy didn't quite fit. Part of it was physical: young Nancy in the comic book is a skinny little kid with a narrow face and big eyes. In retrospect, probably no living child would quite look right. Maybe a girl who'd just gone through a growth spurt -- you know how kids can be, when they grow six inches in a year and don't gain any weight to compensate. Ms. Alba is fairly attractive, but she's on the thin side, while adult Nancy from the comic is more curvy.
Frank Miller also drew many loving panels of Nancy Callahan, who works as a stripper, dancing in a strip club. Ms. Alba declined to go topless for the role, which made these one of the few scenes that stand out as not matching the comic book.
But even if she had been topless, the visual match would've still been missing. It's clear from Miller's drawings that he meant Callahan to be able to dance. Not merely "dance like a stripper" but to have the kind of stage presence that drew the eye and commanded attention.
Ms. Alba, by contrast, danced like a stripper. An attractive but ordinary stripper. I don't think this is the actress's fault: apparently Rodriguez wanted her to look "natural", so instead of choreographing her moves, Ms. Alba went to strip clubs to see how strippers danced, and patterned her act accordingly. I think this was a mistake on the director's part, personally. Someone could've at least taught her how to twirl a rope. :)
This was a hard movie for me to watch, especially the second half of "Yellow Bastard", the story that concludes the movie. Most of the characters in "Sin City" are anti-heroes that are hard to feel close sympathy for. The protagonists aren't the worst characters in the stories, by any means (the villains are really twisted people). But they're mostly a lot of brutal misfits that don't feel like they'd fit in even if they weren't pushed into such awful circumstances.
Nancy Callahan and Detective Hartigan, however, have always come across to me as basically good people stuck in a terrible situation and doing the best that they can. unlike Marv, who hacks through everyone is his path with a kind of blithe indifference, Hartigan is fairly restrained. He does sneak up on some cops and kill them, but let's face it: these are cops who are guarding a mass murderer and serial rapist who tortures little girls. They'd have to be working really hard to preserve their ignorance if they wanted to come off as "innocent". So I think of Hartigan as a good guy, and Callahan too. I want things to go well for them, and I know they're not. I knew what was going to happen to Hartigan after he saved little Nancy, and I didn't want to see it. I knew what was going to happen to him after he saved her the second time, and part of me was hoping they'd change the ending. I knew they wouldn't, and for story integrity, they couldn't. But I wanted them to.
"Yellow Bastard" is a powerful story, powerful enough that it's stuck with me for years after I read it. I've read Marv's story, too, and some of the Dwight/Miho stories. But I couldn't remember how Marv's or Dwight's went. With "Yellow Bastard", I could tell at a glance that it was a scene-for-scene exact reproduction of the comic. I remembered it that well. But I almost didn't want to see this movie just because I find it such a painful story. It's hard for me to recommend this movie whole-heartedly, simple because it's not something I really enjoyed seeing.