I *had* a F27 unit that I bought direct from V last December. The set produced the loud buzzing on bright screens, so they sent a tech out to do in-home repair. He replaced the power board (the Vizio tech said the problem was a faulty sustainer) in about 2 hours. After the whole thing was back together with the new power board, the buzzing was actually louder! This was three weeks ago (it took that long for them to get the repair part in). The technician said he would call this back in to V.
Last week, I get a call from Vizio saying that my new TV would be arriving in about a week. Sure enough, it arrived today and I traded my old buzzy set for the new one, a F33 serial (even though it has a August build date, the set was pristine, no dead pizels or retained images from previous use, with no marks anywhere and super tight inputs with no scratches on them -- yeah I checked, so it is a 'new' monitor). Amazingly enough, the buzzing noise was greatly reduced in this set from the last one, enough to where one has to mute the volume and get right up to the set and listen for it to hear. The old set's buzzing could be heard during normal listening volume from my regular viewing position (about 10 feet).
For anyone who dismisses the buzzing as normal electronics noise, I will say that having a buzzy Vizio PDP versus a quiet Vizio PDP is a noticable difference. Yes, there is some noise in the new set, but having to intentionally listen for the buzz instead of hearing it all the time makes a world of difference.