Just want to report that I've had the PND6500 for several months now and it does have a slight buzzing sound.
I am one that it does not distract me though, and quite frankly would have never caught it had I not read about it in the reviews.
I love this set, it is my first Samsung (I shifted from Panasonic which was awesome), and it is my first Smart TV (which I love). I am thinking of joining netflix.
I would recommend it to anyone, and its black levels are not too far behind my Pro panasonic models, if any.