If you are careful to interpret the film correctly, it could be viewed as a cautionary tale of the importance of pastors feeding their sheep from the word of God. Basic bible literacy could have prevented the tragic events in this story. However, the impression that I get from viewing the film is that the purpose of it is to spread anti-Christian sentiment.
I don't know if I would call this film edifying. My church has been accused of being a cult. In general, as far as unbelievers are concerned, Jesus can be seen as a cult leader. Pseudo-Christian cults do exist, and caution should be taken to bring every doctrine under the light of God's word. However, true Christianity bears many resemblances to what is often seen as cult behavior, including obedience, unity, and faith in the unseen. It seems to me that these characteristics of a healthy Christian doctrine are portrayed in the film as creepy and part of the horror of the situation.
Most Christians are in far less danger of being caught up in a cult, and more danger of being caught up in worldly ways and unbelief.
That being said, the film itself was well done, and when viewed through the proper lens, it is interesting and entertaining. I think the acting for the lead character David was very good, as well as the supporting cast.