Good actors and casting. The dialogue I find mediocre or slightly above. What I like about it is the psychology behind it and that it's pretty no nonsense, but it's also unmemorable. I'm no expert in films with exorcism. The only other film I've seen which reminds me of this is "The Exorcist" (1973) which obviously had a lot higher production value. However, this one is no copy, neither regarding the story line nor in its message which is here much more in the spirit of Charles Bronson in his later years (yes, Richard Bronzi is a Charles Bronson look-alike, but he's a pretty good one). Don't take it too seriously and don't expect high art, just slightly above average entertainment.
I've seen several films with with Richard Bronzi, and only "Once Upon a Time in Deadwood" and this one get a small recommendation from me. The others I find a bit too uneven.