I wanted to update everyone on my PN51E6500 that I was pretty hasty on criticizing after I first got it. I've been running content on it for a little over 80 hours now, with only running slides while I'm not watching it. I've actually noticed a decrease in the buzzing during normal content viewing. In 3D mode, the buzzing is still very prominent and can be heard over all but loud scenes. I also picked up the Disney WOW calibration bluray and ran it yesterday. This helped me fix several of the problems I was having with the 3D picture.
I had the TV in 16x9 viewing mode, when it should have been on Screen Fit. When it was in 16x9, it actually distorted and cropped off some of the image, so when I viewed 3D content it didn't align up perfectly. The 1920x1080 single pixel checkerboard pattern was awesome in helping me correct this and to adjust my HTPC display properly so I could view 3D content through XBMC as well. Keeping 3D Perspective set at 0 also helped.
I have noticed a little image retention after leaving it on Animal Planet over night, the logo in the corner stuck around for a few minutes. I was also going through the Comcast OnDemand menu for about 20 minutes one night and it stuck around for a minute. Both times, it quickly vanished by just watching normal content. I also have one pixel in the middle of the screen that won't display the color red. I tried the Disney WOW pixel flipper, but that didn't help it.
Other than a lack of buzzing, the only two things I wish this TV had would be the Amazon VOD app (although, I have this on my HTPC) and audio out through the HDMI. That way I could hear the sound from the SmartHub apps through my AVR. I believe the only way to do this is with an optical cable. I'm still deciding if I'm going to keep the E6500, or try and exchange it, but other than the buzzing it's an awesome TV. The picture, after just calibrating it myself, is nothing short of amazing.