I am also coming directly from a G2 and I must say, the battery life on the G3 is actually great, way better than what I was expecting after reading the reviews. I had my G2 for about 8 months, and I was averaging 45-46H with about 3,5-4H screen time, with everything turned on (from LTE to NFC), screen set to 60%, stock ROM and kernel, never turned off even at night. My usual drill was to charge it every two days (48 hours), i.e. every second night. Mind you, the G2 was in the QuickWindow case since day 1, and this probably did make a difference (positive).
With the G3, with the exact same conditions (everything turned on, screen set to 60%, stock ROM and kernel), even from my 2nd charge I managed 42+ hours, with SoT between 2,5-3 hours (cant remember the exact number). And that is without the QuickCircle, which I just bought.
As expected, the G3 does not manage the same battery life as the G2, but comes pretty darn close. Taking into account the 5,5" QHD screen and the 2,5GHz of the SoC, I would have to say that this is pretty amazing, all things considered
LG G3 32GB - Life's Good (and stock...for now)
Asus Transformer T100 - Amazing little thing