It's not mainstream enough. The critics at Cannes went crazy over it, so it appeals to the highbrow set who'd normally turn their noses up at anything with action in it.
The violence is said to be extremely graphic (to give you an idea, the director, Nicholas Winding Refn consulted Gaspar Noe on how to approach the violent scenes. If you've seen any of Noe's films, you know what to expect), and the car chases top anything in recent action films. The whole tone of the movie owes more to '80s action flicks than to what we've been used to in a typical action film. That means No CGI.
That clip I posted is one of the most exciting scenes I've seen in a long time, and the great thing is that nothing really happens in it.