Plot Hole
Spoiler Warning!
Okay, just saw this. If I have this right, at the end it is revealed that all 4 guys except Vincent are in the Loft in the morning and think there is a dead girl laying on the bed with a bunch of pills all around. Luke thinks he killed her the night before but is leading the other 3 to believe she committed suicide. He then shows the other three the DVDs he took of Vincent having sex with their wives so they will want to hatch a plot to make it look like Vincent is connected with her death. So they all agree that Phillip will cut her up, they will drug Vincent, and then handcuff him to the bed so he is connected with her death. (Unbeknownst to the other 3, Luke is going to make it look like Vincent murdered her by getting rid of the "suicude" note he had faked up. The other 3 just think Phillip will be connected to a suicide.) Phillip being the sadistic guy he is goes wild with the slashing.
But then it turns out she isn't really dead when Phillip slashes her, so Phillip actually killed her.
There is big plot problem with this. Surely these guys (who all seemed fairly intelligent) would have known she wasn't dead. A dead body would be cold, and rigor mortis would have set in. Of course, if she had been dead, there would be no bleeding when her wrists were cut. The movie wants you to think these 4 guys all thought you can cut the wrists of someone who has been dead for hours and make it look like she bled to death.
Admittedly, I may have missed something.