I have used OxygenOS 4.1.3 for about 2 weeks and it has won me over. It is a battery sipper. I left it uncharged and overnight it just consumed 2 % (100 to 98%). There is some niggling Mobile Radio consumption but it did not put a dent on the battery performance. This can be a problem.
The phone sleeps so hard, alarms sometimes don’t ring. This is even after taking them out from Battery Optimization. At times, the stock clock app does trigger the alarm, but third party apps like AlarmDroid does not. What I have found, by locking the AlarmDroid app in RAM solves the problem.
Another annoying feature of OxygenOS is in QuickSettings, the status bar icons cannot be click or tap through like in Cyanogen or CyanogenMod.
In another news, the new iteration OnePlus 5 is rumoured to be announced any day now.