Read some posts a page or so back, we are discussing Coherence quite a lot
Agree on the other mentions you have though, with Primer being my favourite.
What I love about Coherence is all the clues, plus the dialogue and whole setting. They really just met up one night and decided to make a movie, without scriptet dialogue etc , and it shows. The dialogue, setting, acting and everything makes it genuinely feel like a bunch of friends meeting up a night and weird shit happening.
One of the few movies I have watched that made me google it and read up a whole lot on the clues and how to interpret etc. after watching it.