Tiny battery combined with untested lollipop = major problems.
Well, this tiny battery has been outperforming my new G4 all week long and that's with a 3000mAh battery.
I bought the G4 last Friday and I'm giving it just a couple of more days, if it doesn't get better it will go back to T-mobile, best battery life since last Friday has been 5.25 hours of SoT with same settings, apps and syncing apps than my S6 edge and with same conditions my S6 Edge has always giving me no less than 6 hours of SoT on Weekends for 2 months now, and averaging 5.25-5.5 of SoT on Weekdays when I use my Android Wear and have the Bluetooth on All day. Best SoT with the G4 during this past days has been 4.75 but averaging about 4-4.25 SoT, with the worst day in years this Monday when I was all day on the road and I got 3.5 hours where my edge has always giving me around 5 hours.
I like the G4, but it is slower than the S6 using same apps, has shown some lags where the S6 has nothing and the battery is the main thing that is making me considering getting it back, no sense for me to pay for a phone with less battery having the S6 collecting dust. It has been best LG to date, but still short compared to the best Samsung phone to date.
Back to the battery life, this experience with tons of others around all the Forums of all devices with Lollipop confirms that this is not a Samsung problem, this is Google's (lollipop) problem and yes, the battery on the S6/edge could have been bigger, but for me it has shown enough proof that they were "almost" right and their processor, Memory and display combo are a killer and even with that "tiny" battery it's outperforming other devices with bigger ones. (If you are not suffering from one of the infamous Lollipop battery bugs)