The plot is nice and I give 4/5 for its concept and few moments of tension. However it is not as smooth and tense as one would like. Biggest problem for me is how it just takes them 3-4 lines out of a book on "current research" to understand what is going on. Rushed the set up imo but after that it is quite rewarding.
It successfully sideswipes with a concept that becomes necessary after the stagey naturalism of the dinner party, extreme zooms and shakey cam that at least feel earned by an improv vibe. At ends with the 'hard' sci-fi of the mechanics, which is more interested in trickery than resolving its emotional conflicts of diverging choices. Clever but I didn't need to revisit after it had revealed its tricks.
Made with only 50K, Coherence is a remarkable achievement and incredibly watchable. It may be rough around the edges, but it's a really fun mind-fuck of a movie that will keep you intrigued and guessing until the very end. Giving the small scope of the budget, the ideas this movie has are massive. While its ambition deserves 5 stars, the craft is at a 2 (can't really blame them for that) and the ending is a mess.