Finally broke down and rented this on amazon. It wasn't bad. It was a movie for intellectual types and featured a cast of characters that had some scientists in it.
Nutshell. 8 friends get together for a dinner party and to watch a comet going by earth.
Something happens, presumably an effect of the comet, and suddenly it turns out that the whole "parallel worlds" thing isn't just a theory anymore.

People realize their immediate neighbors are them. Secrets get exposed as people are saying things they weren't supposed to and tempers flare. (YOU

ED MY WIFE?!?!) No one is sure if the people around them are from their world anymore.
All in all an entertaining movie if you're tired of superheroes and car crash movies. The actors were generally told to improv which gives it a more believable feeling as the actors are speaking for their characters like a
RPG.
Very low budget, but worth a rent. Not one you're likely to watch too often.