I found it very enjoyable. To be honest, I thought that the (SPOILER)"unreliable narrator" aspect was signposted too much, but maybe that was just me. As soon as OA opened her story with 'I'm actually the daughter of a Russian millionaire', I knew something was up
Brit Marling's performance had a bit of a "Keanu Reeves in The Matrix" feel to me: as in, her performance felt a bit flat occasionally, but I wasn't sure whether that was due to the character or the acting.
I totally understand why some people just couldn't stomach it: there are certain aspects which you either just accept as part of the premise of the story, or don't.
My only small criticism is that I feel like it could have gone a bit weirder, specifically in regards to the (SPOILER) imprisoned five's changing perceptions of reality and their place in it. But then, that might just be me being familiar with the genre: I read a LOT of sci-fi, as this fit pretty comfortably into the 'stange event and/or artifact unlocks a new level of human consciousness' category, so it felt to me a little bit like treading familiar ground.