I think saying 'zero buzz' is just as misleading as saying 'buzz at 15feet is normal'
ppl hear differently, and I don't expect any electronics to emit zero buzz. I definitely wouldn't consider my f8500 a 'buzzer'. it's not annoying, it's not noticeable when watching, but it's not 'zero buzz' either. truth be told, if I manipulate the install in the wrong way, I can actually make it sound worse, almost to the point that it is noticeable while viewing content.
anyway, I just think if you expect the tv to be 100% silent, you're going to end up sending back good units. there's a difference between detecting buzz at 15feet, and hearing buzz at 15feet while watching the tv. I definitely would not accept the latter, but I am able to tell whether or not my tv is on by the 'buzz' it makes as soon as I walk into the room, in some cases before. I could do this easily with crt's, the plasmas I've owned have actually been much quieter.
I would compare it to the buzz of an incandescent light bulb, or the background static of a midrange a/v receiver. it's there if you hunt for it, but you HAVE to hunt for it. it shouldn't be as loud or obvious as the buzzing you'd hear from fluorescent lights or a cheap dimmer switch