Watch this movie.
It's fun and absolutely irreverent while being faithful at the same time. The basic plot idea is fairly novel, and works well with the story despite the obvious logical and religious fallacies that present themselves in such a scenario.
In the same way that the "Adams Family" brought a breath of fresh air to the TV sitcom industry, this film brings a breath of fresh (well, freshly laden with the scent of whiskey perhaps..) air to the idea of exorcism. The Adams are evil, dark, twisted and backward, and yet somehow manage to deeply embody the cherished values of any strong family.
This film works somewhat the same, but with a lot more swearing, sexual innuendos and gory battles. The priests are absolutely the worst of the worst, and purposely keep themselves yoked with the burden of as much sin as they can in order to "fight fire with fire." It's a new take on the idea for certain. The originality makes it fun, and you can tell that the writers got it down quick, with all of the energy that having a good idea can generate.
This is a movie that was made purely for the sake of outlandish enjoyment. It has few pretenses, and doesn't bother taking itself seriously at all.
If you don't mind a little swearing, some poking at religion, a few sexual references and some fake blood, then I suspect you will enjoy this movie. So put your cynicism and expectations on the sideline for a little while and watch this. It's a good time.
And if you decide to watch it, know that my personal favorite part was the scene with the cracker.. and make sure you read the credits.