Design/Build
The G3 has the best plastic seen + touched on a smartphone.
Display
Performance/Battery Life
The G3 is powered by our current favorite: the Snapdragon 801 CPU - a quad-core 2.5GHz one to be exact. Rolling side-by-side w/ 3GB of RAM + 32GB of storage. Thanks to LG's UI not being as heavy as TouchWiz, you get optimal performance on this thing at all times. Allowing you to enjoy features like Dual Window and such w/o the fear of dreaded lag or a delayed response. Never had an issue w/ the performance of LG devices and that continues w/ the G3 as well.
Camera
While Samsung has stepped up their efforts in the optics department, LG is still one of the best shooters for Android.
Software
LG has took their proprietary Knock On/Code even better. With Knock On, double-tapping can wake the phone up from sleep or put them back sleep on a blank screen. As HTC attempted the same feature on the M8, it works as beautifully as advertised on the G3. Knock Code gets improved w/ adding more ways to unlock your phone by tapping the display in a specific pattern - think the old-school Simon game. Making phone security more difficult to crack.
Overall, LG's software has a nice touch and will be more loved or less hated. I love all that they have done while others may appreciate it a bit more. Whether you utilize all of the new features on board or not.