I'm seeing issues using headphones also. Someone mentioned static and popping noises?
I have the Sprint version of the G3 and it's not too noticeable when using with passive headphones, but when using active noise-cancelling headphones (ie those separately powered via batteries), the static and popping are extremely apparent and border on painful to the ear.
For comparison, I played the same tracks with noise-cancelling headphones on both my old Samsung S3 and my new LG G3 using the Google music app. Sounds great on the S3 with no interference noises, just the silent hum of the noise cancelling at work. With the LG, unless something is playing, there is a high amount interference. When the track starts, there is a loud *pop*.
Makes sense that most complaints are when running through an externally powered speaker like a car or powered headphones.
I sure hope this isn't a hardware issue. I use my phone for music all the time and the G3 has made me want to listen less and choose different headphones.