I know this is an old thread but I had to resurrect it because I just watched The Devil's Backbone and I thought it sucked.
For a start, it's hardly a horror movie. The little ghost boy doesn't actually do anything one way or another and is completely superfluous.
Also I very nearly switched it off after about half an hour of nothing remotely interesting happening. I stuck with it while it dragged on and on though only to find it had the thinnest storyline of any of Del Toro's movies. There was even less to this than Pan's Labyrinth and that's saying something.
Now the acting was good, the camerawork was good and the one scene where the truck exploded was fantastic but it didn't make up for it all being generally boring.
I've started to like a lot of the Spanish horror movies lately and Spanish cinema overall now it's all started to move away from everything being filmed in various shades of orangey-brown. I was therefore quite surprised that I hated The Devil's Backbone as much as I did.