FWIW, I watched Dredd last night in 2D on a 100" Stewart Firehawk + Sharp Z-20000 + Oppo 83, and I thought the both the movie, and the picture, were fantastic. I had no prior knowledge of "Dredd", had no preconceptions, and found the movie unrelentlessly entertaining, and particularly enjoyed its uncompromising, hyper-visualized violence. IMO, it doesn't matter if you classify it as "Sci-Fi" or not, as it stands on its own merits. Highly recommended.
Regarding the picture: From shot to shot, there are pronounced variations in the image, from smooth and very detailed, to grainy and rather noisy, which are obviously (to me) purposeful, artistic transitions, meant to occasionally convey the grimy world the story takes place in. I enjoyed these transitions, and would have found the movie too 'sterile', for lack of a better word, had the entire movie been shot with a more consistanly smooth image.
Regading the soundtrack: Nothing short of DEMO quality. Period.