I think a lot of people didn't pay enough attention to fully understand and appreciate the ending.SPOILERS AHEAD
A lot of people didn't understand the brother character at all. They don't realize that he says its all good between him and the exorcist (after seeing he's a phony) because the brother was a part of the cult and did not want the sister exorcised for real.
Yeah, I agree, it seems a lot of people (and even some of the people I went with) totally forgot about him by the end of the movie.
They also don't understand the the genious of the whole, this girl could possibly be crazy and not posessed aspect of the plot. At times I found myself second guessing weather or not she truly was posessed.
Yeah, my sister and I agreed that nothing in the movie really pointed to her being posessed, but being a psychology student, I think schizophrenia and DID made sense to me that other people wouldn't understand.
Another thing I realized after finishing the movie is that the reverend at the end restored his faith in god. He went in with that cross voluntarily realizing that since this happened that god was real and would (hopefully) give him the stregnth to kill whatever the edited was in that fire. And I have to admit the dude with the axe chopping up the camera lady was pretty awesome.
I think he lost a little bit of mental stability, but I think it was the result of the trauma of what had happened, that made him believe he truly did have the power of God on his side.
The ultimate reason I would say people don't like the ending though is not because it was bad, it is because it has been completely overused recently. I mean with cloverfield, the blair witch, (haven't seen quarintene but was told it ended the same way), people are just sick of movies where you "make your own ending." It is almost just becoming to cliche for a movie to end abrubtly with no closure.
I disagree, I don't think it was a "make your own ending" in this case. I think it ended just where it should have and that thinking further than where it did end is pointless. I found the ending to be, just that, an ending. There are unanswered questions, yes, but I don't think it's really necessary to answer them. (I guess it kind of also helps that I haven't seen any of the movies that supposedly also have this ending.)
One last reason I didn't completely like the whole film was because a lot of the good parts including the ending and the spoiler of killing the cat where in the trailer. I knew 1.There would be a second exorcism 2. She would kill the cat 3. That there would be some sort of large fire. I was waiting for the fire the whole time only to find out it was the last scene in the whole movie.
This makes me glad I didn't watch the trailer beforehand. And then when I watched it afterward, I was like 1."This doesn't actually look very good" and 2. "What the heck, they spoiled so much!"
Just my 2c