The reviews on this app are loaded with low ratings. I didn't see any from a Nexus 6 customer however. The app never shuts down on you?
Yes that's the one it has more features than most other cameras I've tried and it also takes pretty nice pics. my secondary camera is always manual camera though can't go wrong with that.
I use the paid version. Not sure which reviews you read. Its never shut down on me on my n6. It wasn't that great on my m7 or m8 but great on my n6.