I'd like to see everyone's best arguments here on whether it is the Devil in Batman or a dude claiming to be the Devil.
In a sec, I'll post my current take on the whole thing (after the fold for spoiler's sake)!
Okay, I've become convinced that yeah, it is almost certainly the Devil. I don't think it HAS to be the Devil, and I basically agree that it really does not all together super duper matter if IS the Devil or a dude CLAIMING to be the Devil, so if it turns out NOT to be the Devil, it's not a big deal.
However, upon thinking about it, the deciding factor was whoever I read somewhere that brought up Gothic. In Gothic, Batman fights the Devil, who possesses people. Well, that would work here, no? If Dr. Hurt is actually the loser actor Batman claims he is, but possessed by the Devil, then doesn't that follow perfectly? And doesn't it follow that R.I.P. would involve something 70 years in the making (as Morrison mentioned somewhere) if we reveal that the Devil was involved in the murder of Thomas and Martha Wayne? Heck, you can go one step further and say that the Devil possessed Joe Chill!!!
So yeah, while I'm not COMPLETELY convinced (and, again, I don't think it is a huge deal either way), I think it IS the Devil we're dealing with here.
And the notion that the Devil killed Bruce Wayne's parents to drive him to the "dark side" only to see him defy him and become a force for good, so the Devil comes back years later to try to turn him again, even overtly saying "If you do not serve me, I will ruin your parents' good name," and Batman STILL defies him?
That would be awesome, if that IS the case.