Honestly, I thought this was on the VERGE of being pretty good. Does it have limitations? Sure it does: shoestring budget parlayed into sub-par special effects, unvetted aspiring actors, overly convoluted script, awkward directing in places. All that being said, this movie does one thing which I really really like in horror films, which I seldom see: it throws a stack of characters into a panic scenario where they all separate, are fending for themselves, and slowly one by one they're pulled into the reality of the situation. It's hard to describe exactly the atmosphere I'm talking about here, but basically, a group of people who all get separated, and befall misfortunes one by one. There's a very moody atmosphere to this type of concept which I like a lot. Another film that conveyed this pretty well was "Session 9."
The director had a clear vision of what he was doing, and I think it's unfair to say that he wasn't at least semi successful. For one thing, I thought the mental disorder of the protagonist was very well handled. As someone who's been closely involved with people who suffer from extreme hallucinations, I appreciate how this plot point was worked in to synchronize with the characters around the protagonist. It really annoys me when you have a character who's dealing with this, and it's like they can flip it on and off when it's convenient, and nobody around them notices anything askew.
So, do the films strength's make up for the weaknesses? In my opinion yes. A lot of people seem to think the actors are horrible. Some of the characters come across as a little cliched, but honestly none of them bothered me that much, in terms of acting, speaking only for myself. In the end, I think there's one major point of focus which screws this film up in a bad way. The director leans towards giving it a mystery vibe rather than a thriller vibe, and as such, the plot comes across as convoluted in a way that's disconnected and distracting. The vague "Psycho" reference of the fly shows you sort of where his head was at.
If the director started out by putting everything on the table, and making it a more focused character study like say with Jack Torrence in "The Shinning", I think it would have done leaps and bounds at better selling the premise. The plot points do come across as forced and cliched, largely because the character seems too disconnected from the backstory. It's like a spy movie where the spy saves the day by manually flying a plane, or something of the sport, or just by chance, he knew the main terrorist since childhood, and thus is able to talk him into a resolution. We're supposed to take it for granted, but it comes across as very convenient and inorganic. You'd think the character himself would be a little more aware and calculating, in terms of what was unfolding but no; it comes across as an unfolding mystery to him as well, which doesn't quite fit with what's really motivating him here.
Personally, I'd have liked to see the initial abduction of the crazy religious girl, for example. Didn't really need a whole mystery around it. Just put all the cards on the table and build up that backstory; we already kind of know what's going on anyway. Taking everything into balance, I still thought the film was passable. It does just enough to be credible in its own right. You could definitely do worse, and I think this is not a bad first attempt for a fledging director. All it needed, in a phrase, was tighter execution.