Not without its flaws, but a cut above most horror films8/10
For the most part, films which were intended to frighten the viewing audience usually succeed in instead producing involuntary laughs. So it was nice to see a 'horror' film that not only has a brain for a change, but actually succeeds in being frightening. It may help that the film is allegedly based on true events, which gives credibility to the storyline, and prevents the movie from having those annoyingly gaping plot holes. And indeed, the heading "Based on a true story" doesn't come off as a glaring lie. There are indeed events happening in the film which are questionable as to whether they actually occurred in real life, but the beauty of 'Emily Rose' is that most of the film is retold by various characters, so the events described are as the character perceived them. In this way, the film doesn't distance its audience by declaring that "well, demons were in the film which was 'based on a true story', so demons must actually exist".
But in many ways, 'Emily Rose' is different from almost every past horror movie in the sense that it doesn't make really obvious attempts to frighten its audience. Instead, director/co-screenwriter Scott Derickson seems content to make us think. There are several questions raised in the film regarding religious beliefs and the public's general perception of them, but these are all handled in an objective and impartial manner. And as for the scare factor, since the filmmakers aren't overly obvious in trying to scare the audience, the film actually is frightening at several points - again, unusual for a horror film. The frightening events regarding Emily Rose's exorcism are all the more frightening as they don't seem horribly staged and predictable. (although the cheesy demonic animation, as shown in the trailer, could have been done far better) It's true that composer Christopher Young seems unable to resist the horror movie cliche of having horribly over-dramatic music which builds to a climax at the most frightening moment, but for the most part the movie is able to surpass the usual horror cliches.
It helps of course that the cast all deliver quality performances, the obvious standout being Jennifer Carpenter as Emily. Her possession scenes are nothing short of incredible, the sheer torment she seems capable of portraying is utterly captivating. Laura Linney also shines in the lead, giving a powerful and affecting performance as the attorney of the convicted priest who performed Emily Rose's exorcism. As said priest, Tom Wilkinson also manages to impress, delivering a quietly effective and very human performance. My only complaint is that the characters of Campbell Scott and Colm Feore were really badly written, coming off as the typical antagonistic figures, and nothing more. Both give satisfying performances, despite their one dimensional characters, especially Feore, who has always been talented at taking terribly written characters, and giving them life and personality nonetheless.
So The Exorcism of Emily Rose may not quite be the very best of its genre, but it certainly proves to be one of the more intelligently made ones. The director seems to have for once taken that extra step, and put aside the endless thrills and shocks in favor of making us think a bit. There are some cheesy effects, such as the demonic visions, but there are some genuinely frightening parts, especially the actual exorcism scene, mainly due to the chilling and captivating performance from Jennifer Carpenter as the title character. The principle cast members, Laura Linney and Tom Wilkinson also give strong performances, bringing many layers to their characters. Quite the quality piece overall, and one worth seeing.