Sorry if this poster got your hopes (and other things) up...
Now, even though the pretext for the actor change is that Dwight gets reconstructive surgery on his face, what's hilarious is that they show that in this movie, AND they show its after-effects, so you get to see Brolin with Clive Owen-like prosthetics in a scene or two. No, he doesn't try to do the voice. Probably for the best. Definitely for the more amusing.
So let's deal with the one area that departs significantly from recreating Miller's drawings - Nancy Callahan is supposed to be a stripper who's naked for most of her comic-book appearances; in this movie, we see Jessica Alba complete an entire dance routine at her club without shedding a single stitch. Given the way Sin City residents resort to punching and shooting at the drop of a fedora, it's hard to imagine these patrons wouldn't feel cheated - and many fanboys definitely do. At the recent Los Angeles press day, Robert Rodriguez (who again codirects the movie with Miller) addressed the issue head on by saying that he knew Alba wouldn't go topless, but he wanted the best actress for the part, and that that was more important. (Miller, in a rare show of possible political correctness, voiced his support for this decision.)
Four seats down, Eva Green and Josh Brolin - both of whom bare almost all in this film and others - did an admirable job of not facepalming.