Best Buy delivered my PN50C450 this morning (version NY02, build date Feb. 2010, Tijuana, Mexico). I waited with baited breath as the techs put the stand together and set the TV in place. One of them pressed the remote's power button, and the set sprang to life - no buzz. I stood next to it as we were talking, and I couldn't hear anything except the low volume of the program. I figured if I got a "buzzer", it would be loud enough for me to tell immediately.
After the guys left, I muted the sound, walked all around the living room - nothing. When I stand right over the set, I can just hear a faint electrical hum, much like a CRT (as some others have stated), and that's it. FYI: My living area is an open floorplan with the kitchen, and we just got a Samsung fridge that has the usual "fridge hum", and we have a freezer in the adjacent utility room that makes the usual "freezer hum", so maybe they are masking the sound. I did close the utility room door, and quieted things down some, but I still couldn't hear anything from the muted TV.
In any event, I am hopeful that the problem that some have encountered with buzzing sets is evident from the get-go, right out the box, and not something that develops over time...I really like the set so far, and for the money, it's a deal!
EDIT: I forgot to mention that I noticed after the delivery guys left, the ferrite chokes were still in the bag, so the TV is currently operating quietly without them. I think I'll probably put them on, though.