Can't understand why "accident" confuses everyone (SPOILERS)

Except we clearly see one demon talking to him on the phone, so we know they were real and he was not making them up.

I like that theory. I saw it as a simple hit and run. I think in reality he drove away when his wife called as its after that he calls 911 and everything starts going tits up. He was on his phone while driving and chose to drive away but he isn't actually a thoroughly evil person so the graphic way he has to try and save her is his punishment. He would have saved her but was more afraid of the consequences to his own life. If he chose to call 911 again at the end instead of leaving in a new car to restart the cycle he'd "win".

Since I had no idea what was going on, I'll go with your story.

Wow what a bunch of bullcrap. You are absolutely wrong and so off base.

He made the morally 'RIGHT' choices, that moment where he's deciding what to do and instead of fleeing he calls 911. Yeah he was neglectful driving, he hesitated to dial 911, didn't attend to her needs quick enough and was at least partially thinking of his sake but he does the right thing. He does his best, tries to save her life and she dies.

Unlike all the other characters, he seems to bypass the punishment of purgatory and death. I say seems because you never know, they may have been playing him still and had tortured him some more or for eternity.

As for the laughter, they're earphones dummy! of course he can still hear it if the sound coming from them is loud enough. I can hear mine if set them down and jack up the volume.

I read it as his hell/purgatory where he had to replay this accident. He probably ran into the girl in real life, saw that she was close to death and drove away. This is his penance or punishment in death. He tried to help her this time, even if he failed, so maybe he is changing and might atone for it?
That's my read on it. :)

I agree with AgentPhantom's description above, although I would certainly have written the post more diplomatically. But that's just me, always hoping for Internet discourse that's more courteous and less insulting. I know, dream on, right? Still, one can always hope.

All that said, yes, the driver was the ONE guy in the film who did the right thing. He was in the middle of nowhere and he could have bolted, but he didn't. He does his short stint in purgatory, having to live with the moral consequences of his actions, having to suffer emotionally with the death of the girl, and then he gets to move on, otherwise unscathed. He's the only one who gets away in the end.

I don't think the 'serial killer' explanation works all that well... particularly in the context of the rest of the movie. There's nothing to suggest the guy has killed before, or that he means the girl any harm or enjoys her suffering.
He's guilty of manslaughter... his selfish stupidity killed her... but if I allow the movie to be a tad less black/white moralistic than some seem to be taking it then I don't think he was 'let go' because he 'did the right thing'. The girl is still dead and its still his fault. The demons/whatever enjoyed toying with him and in the end he accepts their aid, including promises that no repercussions will come back on him. This suggests he's still a deeply selfish person, only looking out for himself.
Maybe I'm just kidding myself that the movie isn't so simplistic as the trite 'evil doers get punished and the repentant are allowed to leave' morality nonsense.

I actually liked it(not enough to watch it straight a few times unless 10 years from now when I forgot about what is was).

Didn't like the end though our it would had been better.