In many ways, there's very little to Sin City, but that doesn't stop it from being stunning. The film is all spectacle; it doesn't flag for a second, and packs a mighty punch - the action is comic-booky and so both spectacular and visceral. Its universe is a harsh, individualistic one, but there's a morality of sorts of play, and indeed it's the implicit moral choices made by the characters which drive much of the action forward. I don't know much about the noir genre, but doing a whole film in black + white, with only the occasional splashes of red and yellow and blue-grey-green eyes, and setting it seemingly exclusively at night, must be a good start, particularly when taken with the hard-boiled dialogue (and voiceovers) and frequent outbreaks of violence. The film is pulpy in feel - there are basically three completely separate narratives, more or less related one after the other - but it's all part of the effect...
I also thought that all of the lead actors (primarily Willis, Rourke, Owen, Alba and Del Toro) were very good - striking the right notes and sustaining them from the get-go. The support cast was uniformly good, too (Elijah Wood stood out as the absolutely terrifying, spidery 'eater of souls'). And the city looked just right - not ostentatiously gothic or baroque in its layout and architecture, but all shadows and alleys, urban dystopia writ large precisely because done in such muted, accretion-of-everydayness style.
On a different note, I was bemused by the way in which Sid completely ruled over me in the medium-famous celebrity identification stakes - variously, he was excited about Jessica Alba, recognised Josh Hartnett, and actually knew who Alexis Bledel was - although, thanks to David's repeated mentioning of the 'lesbian Charlie's Angels film' and my consequent googling of that very phrase to learn that the film in question is called 'D.E.B.S.', I was at least able to pick the sword-wielding Japanese prostitute as Devon Aoki...