This is a strong movie and it needed unknown faces/actors, to get you sucked in to the whole thing. And while this is a one location movie, the intensity is there. It's not easy to watch and I would call this anything but entertaining. That being said, it doesn't make it less of a movie for being brutally honest with its characters.
And it's not an easy task to achieve. You have to be careful not to glide into cliché territory. To lose the audience either because you're too soft or too gross/vivid with what you show. I think the movie walks that line and achieves it. It's small budget of course and there are restrictions, but all being said, this is what it it's supposed to be. Can you handle it?