Improvised Dialogue=People talking over one another=incoherence=audience irritation

Quantum decoherence and the many-worlds interpretation that accompanies it is a fun subject to tackle in science fiction. Unfortunately, this is not the movie to watch if you crave an exciting narrative to go along with it. In writing fiction, the first rule is "Show, don't tell." This is especially true of screenplays. But because this movie had an uber cheap budget, they had to spend the majority of the movie talking about interesting ideas rather than showing us. Also bad, out of focus camera work, improvised dialogue which included annoying people talking over one another the entire time and a contrived plot/conflict.

It's all well and good to have one character, Mike, who has a drinking problem and such hostility toward himself that he assumes that his Doppelganger will try to kill him. But why are all the other characters in this film so paranoid and on edge from the beginning? They're a bunch of self-absorbed yuppies, not escaped murderers from a maximum-security prison.

You're at a dinner party, there's a power outage so the lights go out, and then there's a knock at the door so. . . you startle as if they threw a rock through your window? And then grab a baseball bat before answering? This seems odd, especially when two members of your party have just left to go investigate the house up the street with the intention of asking to use the phone. If it were me, I'd just assume that someone was probably coming to my door to ask the very same thing.

And once these characters figure out that reality has fractured and that there are duplicates of themselves from another reality running around--I still don't understand what they're so afraid of. I mean, obviously, that would be a freaky and unsettling situation. But once your doppelganger has demonstrated, by leaving exactly the same note that you wrote on your front door, that he behaves exactly as you do, wouldn't you at least be somewhat curious to meet him or her? Most of these characters seemed reasonably intelligent and rational. Why should they be so automatically fearful of these alternative selves--even after they've accidentally spent time with them and found them to be benign.

I think the writer needed a stronger trigger for all the fear and hostility.

If you like the subject matter and want to see people talk about it, search for lectures on youtube. If you want good sci-fi that deals with the theory, check out Fringe or even The Twilight Zone.