Going from a Sony Xperia Z1 to the G4 has not been a fairytale story as far as I'm concerned.
Battery life seems very bad in comparison, stabilty is not good at all.
The days that it is working though, it's magnificent. Camera are the best I've seen.
If the problems that I see with the phone does not better with the M update, I'm starting to doubt the G4, or Android as a whole. I haven't had the opportunity to try the other flag ships on Android, but does anyone know if they have the same type of problems with L and M? My Z1 was on Kitkat and was smooth sailing. After I upgraded that one to 5.1 it started having the issues that I also see with the G4. So I downgraded that one again and gave it to my gf. Other than the fact that the screen is a hell of a lot better on the G4, the Sony is still operating much better than the G4.
And that should not be the case when you spend a good amount of cash on it if you ask me..