Well, it's been over a week and I'm still on the official Marshmallow, unrooted. I haven't gone to rooting as so far, I haven't needed to do so.
Battery life, coupled with Doze mode, SnapDragon BatteryGuru and Greenify (yes, I can still use this unrooted - I just do a greenify before I lock the screen), I get through a day without issues (as long as I'm not playing long sessions of Game of War or Mobile Strike). At night, when I go to bed, Doze mode takes over and I either lose 0% battery or maybe 1% or 2% at the most.
The only issues I've run into are with two apps:
- Alarm Clock Xtreme - this will not go off after Doze mode kicks in. I've even told the battery optimizer to not doze the app, but it still doesn't work. The company that owns the app has admitted that the app is not using correct Marshmallow API practices for an alarm clock app. Either the stock alarm is fine, or do as I did and switch to Simple Alarm Clock. I want the increasing alarm volume option that is present in this app and Alarm Clock Xtreme. The default app jolts me awake since it starts the alarm at full volume. I don't like that.
- Game of War - I've noticed that with any keyboard (stock LG G3, Swiftkey, Google), that when I am typing in a chat input box, the game no longer moves the chat input box to the top of my keyboard, so it's obscured while I'm typing and I can't see what's being typed. Mobile Strike doesn't do this nor any other app. I've sent that issue into MachineZone and they've forwarded it onto their developers.
Other than those two issues, the phone is awesome. Much better than Lollipop, and I wasn't having any issues under stock Lollipop except battery life wasn't as good as running Jasmine ROM. But, with MM, I'm getting much better battery life stock and unrooted than I did under LP.