The audible buzz on my set is inconsistent and infrequent. It does have a constant low level buzz, but you have to put your head behind the screen to hear it. Once you're on the couch it's impossible to detect. If you enter the browser it buzzes on the white screen but stops buzzing once you direct it to a web page.
If any ambient noise is present, such as air conditioning or a dehumidifier, any buzz (even the loudest version) is impossible to detect even when the set is on mute. On my TV the volume threshold for detecting a buzz is 8 (HW-H550). as soon as I go above that level any buzz (when it occurs) is effectively eliminated.
My unit never seems to buzz when it matters. I had a friend over last night to show off my set (Prometheus and Tron:Legacy) and the audible buzz never showed up. Not at powerup, and not during the setup, menu screens, or playback (Samsung owes me; I think I sold him a TV). However, a few nights ago I dazed off watching Netflix, and when I woke up I was startled by the loudest buzz Ive ever heard the set emit (it didn't help that the house was completely silent). Strangely, it was occurring while the TV was in screen saver mode (black screen with the Samsung icon bouncing about). As soon as I pressed the button on the remote to go back to regular TV the buzzing disappeared.
I'm compulsive about this sort of thing, but even for me the buzzing issue is receding by the day and by now it's gotten to the point I no longer think or worry about it. Its truly a shame that many people looking for a great HDTV will research the f8500 series and be put off by the many "buzz" debates they'll find on the web. It's not a big deal at all imo. Like bezels on a multi-monitor setup, it's chiefly an issue for non-owners wondering about it (most, anyway. I'm certain a few sets buzz louder that the rest, and some very sensitive ears surely exist out there).