I think this movie would have been twice as good if only it had half (or maybe 1/3?) of the violence. - And of course, if they got rid of all of the (extremely unnecessary) drug use.
The idea is a cross between brilliant and psycho, and it's sickening all the violence.
Definitely NOT for anyone under the age of 16 (I mean, hey, it is rated R so that tells you something).
To tell you the truth, I would suggest searching for the cute parts with Sam and Emily...not sure about all of the driving scene though, that's gruesome.
Hurts to rate it so bad when I love Karen Gillan so much...(and her character)
But as my teen brother said, 'It would have been better if they ended it by morally cleaning up some stuff' (aka talking to Emily about violence and the importance of human life).
So what am I saying?
Don't watch this unless you just love Karen Gillan (yeah that's me) and your willing to miss some of the movie because you can no longer handle the gore and have to look away.