I finally decided to go for a blind buy on this one! I watched it yesterday. By the way, the canadian Blu-ray doesn't mention nor include more than one cut. After verification, it IS the uncut version, with a running time of 102 mins, while the cut, R-rated version is 98 mins. After reading some of the comments above, I must say I'm a little surprised by the overall reaction, nothing really shocked me in this movie. I thought Matthew McConaughey was great (as for the "full frontal nudity" from his part mentioned earlier, 1/it's not "frontal" 2/it doesn't last more than a few seconds, I fail to see any problem here), and I am so, so glad he's taking more serious, challenging roles now. The rest of the cast was more than good too, especially Gina Gershon, Thomas Haden Church and Juno Temple, in a role that added an ethereal, hopeful presense to the whole thing... For people who like Tarantino's humor, or twisted crime thrillers this one shouldn't disappoint. I liked it a lot. I didn't find the violence gratuitous in the least (same for the nudity - which again, even for the other characters besides McConaughey, just happens in a few scenes ONLY), just in line with the characters, who don't have any sort of moral value whatsoever, therefore concepts like common sense and normality don't really apply to them. A lot of funny moments as well.
Finally, after seeing it, I think it should have been rated R, not NC-17! It kind of adds a superfluous "watch at your own risk" label to it for no reason. Yes it's violent, it tells a weird story, it has nudity (oooooooooooh the horror!), so what, nothing that we haven't seen before if you ask me. A film like Drive might have less boobs in it, but it has the same amount of weirdos (or at least similar ones)...
 it should be noted that the film is no longer rated NC-17, but is now UNRATED (which explains the 'unrated' director's cut Blu-ray, which IS the previous NC-17 version)
From filmratings bulletin #2246:
Edited by Morpheo - 12/30/12 at 9:22am
NOTE: THE NC-17 RATING FOR "KILLER JOE" (C.A.R.A. CERTIFICATE NO. 47457, BULLETIN NO. 2212 2/29/12) HAS BEEN SURRENDERED. THIS FILM IS UNRATED AS OF 10/23/12.