The Rite
There is, of course, a kernel of truth in the story: the Church does teach that we have supernatural enemies (fallen angels--devils, and demons) and that people are capable of choosing Hell (the souls of the damned); it does teach that Jesus can use ordained ministers (deacons, priests, or bishops) to drive evil spirits out of the souls of God's children; the holiness and wisdom of the exorcist does make a difference in the efficacy of the rite--in obedience to the Scripture passage, "This kind can only be driven out by prayer [and fasting]," the exorcist often fasts and prays continually until the matter is resolved; there is a renewed emphasis on the need for the ordained to be trained as exorcists so that they are available when needed.
Exorcism is NOT a contest between the exorcist and the unclean spirits. It is the application of Jesus' victory on the Cross to a suffering member of His Body.
Because the movie was designed to make money for the producers, I doubt that it is an entirely accurate representation of the Church's teaching. Some day I will go see it, I suppose; it is not something I look forward to at all.