'Coherence' is master example of what you can achieve with close to no budget, but enough inventiveness. Shot over five days with almost unknown cast (except maybe Nicholas Brendon from 'Buffy the Vampire Slayer') and mostly improvised scenes and dialogue. The writers (director James Ward Byrkit and Alex Manugian who also played the role of Amir) had only written just story and established rules while most of the witty dialogue were improvised by actors themselves, thus proving that the film doesn't need some superstars, but rather talented ensemble cast. Although the hand-held camera-work might seem to take viewer out of the story, it was just another way to give more room to the improvisation. Despite all of that the film manages to keep an eerie atmosphere, and the story movies on one continuous flow without getting sidetracked. The story also doesn't crumble into pieces under it's own ambitions. The twists hold together and actually makes sense. Although the final twist might seem to be rushed and thrown into there just for the sake of it, but it kinda fits and doesn't change the film's overall tone.
'Coherence' is slow burning psychological science-fiction for a thinking person, and it holds up much better than most big budgeted pretentious science-fiction extravaganzas. Recommended especially for those who like independent sci-fi and/or films that take place in one room.