Funny thing is this phone had more or less the same bluetooth-audio problems in 4.2.2.
However when I did the update to 4.3 on the HTC One the sound quality became perfect! I also installed 4.4.2 recently on the HTC, but sound is still great whatsoever.
So if HTC didn't fix this in 4.3 by themselves, its probably a bluetooth-fix coming with 4.3+, which means ppl just have to sit tight for official 4.4.x or use CM11 meanwhile.
Offtopic: I don't really miss the LG G2 luckily, HTC One feels more premium in hand and the UI is very fast and well designed. The loss of better hardware specs is just some words on a paper. Hell, I would say the HTC One even feels snappier!