I appreciated the unpredictable swings the film's script took and the unconventional structure but something in the direction really killed the tension in a few key places for me. Though it seems there are some spoilers here already I like to be polite, I can't imagine bothering to watch this at all if it's been spoiled...
Spoiler
The second half of the film is obviously the controversial part and it's where the fans and detractors surely part ways. The crucial misstep here for me was that, again, the twist the plot takes when Anna is handcuffed was a shock, but the film gives away too much too soon. When the older woman explains the martyr images it's completely obvious that Anna will be tortured and become the martyr they're looking for, there's nowhere else for the film to go. During the half hour or so of repetitive torture my mind wandered a bit since I knew where it was leading, which gave me enough time to speculate that the only reason you would want to put someone into this state would be to try and learn about the afterlife, and lo and behold, that's exactly it. When people start showing up for the press conference it's pretty clear that we won't learn what Anna actually said since I doubted the filmmaker would be ballsy enough to try and answer this eternal question right at the end of his film, and we're left with the open ending.
The ending is the thing that both completely makes and breaks this film for me. It seems to me that the Mademoiselle couldn't have learned that something good lay beyond or she'd have told her followers instead of eating a bullet. Both killing herself and her last line of dialogue ("keep doubting") seem intended to both atone for her sins or imply her failure to cope with the knowledge she has (or hasn't learned), and to stop her followers from continuing the search so they don't wind up like her. Ominous words and your leader's suicide are pretty good deterrents. That means the only real answers seem to be that she either heard that there was nothing beyond (i.e. the atheist reading), she heard something she couldn't understand (i.e. the agnostic reading), or she heard that there was something bad waiting for her (i.e. the religious reading). You could also get into the argument of whether Anna could have lied or not, but that doesn't seem to have any real bearing on the picture either - if she managed to get her revenge by lying she still seems to have come out of the whole thing far worse than the perpetrators. The film doesn't make any sort of stand or claim here whatsoever to defend, it doesn't engage the idea at all beyond raising the question. I'm not sure that's enough to justify sitting through all that torture for.
At the end seeing this movie is something like someone tellig you in middle school that they know a girl who has a crush on you but will only tell you for a dollar - after taking your dollar to the snack machine they back out on the deal and don't tell you anything. You're left angry, you feel a bit cheated, your probably won't want to talk to that person again, but worst of all, you've had your curiosity piqued about this girl who you've learned nothing about, if she even existed at all in the first place.