I bought the G3 last week and will be returning it.
I love the phone. It has a big, sharp screen in a beautiful, easy to hold body. Camera is excellent and performance it is pretty snappy especially when using a launcher like Nova. The UI is good, but not great...way better than Touchwiz, but not as good as stock Android or what you find on the Moto X. The phone is just fun to use and I don't want to return it.
BUT, on the third day of use I got the dreaded "overheating" warning. I was at the beach and decided to put the camera and video on my new phone to use. It was sunny and bright outside so I cranked up the brightness to 85%. I took a few photos and started recording a video. About 10-15 seconds into the video, recording stopped, the screen dimmed, and a message popped up about the heat and having to cool down. I didn't get a great look at the message because it was so quick and the screen was dim, but there was a message in the notifications panel about having to cool down.
This was incredibly disappointing as I have done this exact same thing in the same scenario with different phones, but had no issues with overheating. I haven't received any overheating warnings since then, but I have experienced some screen dimming while outdoors or in a car in warm conditions.
I love the phone, but the overheating and screen dimming really turned me off and I don't want to be stuck with a device that fails in moments when I want to take advantage of its features.
I really feel that if LG had gone with a 1080p screen, this would be the perfect phone I was hoping it would be. Unfortunately, I have to keep waiting!
Sorry that this is more of a "Why Not the G3," but I thought I'd share my experience.