(warning: contains spoilers)
Rating: 1.5 out of 5 stars.
Pro: mildly innovative new ways for people to die.
Con: inplausible plot elements and character behavior.
This movie seems like another Saw (2004) copycat. There is a evil madman with a distorted deep voice taunting his victims and giving them situations where they can presumably escape death by doing something horrifying to themselves. One of the first victims even has to retrieve a key from inside himself as indicated on an X-ray, which is a situation seemingly lifted verbatim from Saw II (2005).
However, I think the movie's real shortcoming is in its execution of this sort of plot. For example, in parallel with the story line following the six victims, there is a storyline of a "boy who cried wolf" cop who is trying to track down this serial killer, and the FBI agent sent to help him. This storyline seems to exist only to add length to the movie, as the cop's only contribution to the plot is to get himself killed immediately upon entering the warehouse to save the remaining victims, and the FBI agent's only role is to.. well, she actually doesn't do anything of consequence the entire movie.
Another bizarre plot shortcoming is the reveal about 9/10 of the way through the movie that one of the female victims and the villain have a history together where she had burned him and left him to die, and he intends to kill her and her mom in some sort of elaborate revenge. However, this serves only to create a very brief role for the victim's mom, as well as set up a short "oh he wasn't really dead" exit sequence at the end of the movie. No explanation was given for the villain's elaborate trap to torture and kill the other 5 victims. Nor does this tie in with the fact that apparently he has done this before, according to hints from the cop and FBI agent.
Lastly, the characters of the movie act in very implausible fashion. For example, one of the death scenarios is where the twin brother and sister are strapped into chairs with these conveyor-belt-mounted drills moving towards them. Each has a button they can use to stop their drill, but that causes their sibling's drill to start again. They are only being restrained by one handcuff and a collar around their neck. They could easily have destroyed the drill contraption with their feet.
Additionally, at the end, we discover (via a news report) that the villain did not, in fact, die in the fire that the last victim had set, but that the bodies of the other victims had all been found in the burned out room. It is pretty improbable that a severly burned villain would, after escaping into the sewers, manage to return to each victim's location, drag them into the burning room, and leave them there, all without the FBI agent noticing anything (she was apparently there all night until police arrived in the morning).
Overall, it was hard to get engaged in this movie and difficult to give it the credence needed for it to be even remotely scary.