Short review of this movie, what they got wrong/got right, here goes-
WRONG - The script (no input from John Wagner and Alan Grant, Steven DeSouza mangling it), the casting (Sly Stallone is too big a star to play Dredd, it should have been Michael Ironside, and Michelle Forbes should have played Judge Hershey), the designs (Judge costumes too camp, Lawmaster bikes look puny and ugly and ridiculous, Lawgiver guns no replaceable ammo clips), the length (96 minutes, for a Dredd movie? It should have been more like two hours, considering the material to work with), and the budget ($80 million was way too much for a Dredd film, meaning it had to be diluted to justify that amount of money, it should have been kept to about $35 million at most and shot in Mexico where it's cheaper to film).
RIGHT - Cinematography (looks gorgeous), music (decent score by Alan Silvestri, but Basil Poledouris would have been better), visual effects (mostly impressive, especially the opening flyover through the city), some design work (the Mega-City One skyline and boundary wall, the ABC Warrior Robot, the docking bay guards, Mean Machine Angel), and sets (both interior and exterior sets are generally impressive).
All in all, I couldn't recommend this movie as a representative adaptation of the comic-book, but as a big, brash, noisy, and visually impressive action flick, it's okay, but it could have been so much more, a 'director's cut' would certainly be a welcome addition, but barring that, save your money, and wait for the upcoming new adaptation 'Dredd' to be released into cinemas in September 2012...