I have a SONY XBrR 1 and Panasonic Plasma TV. The only time I have ever experienced pixelation on either TV is through the OTA antenna. We have DISH Network, and the only time I have ever seen pixelation is when something was recorded on the DVR during a terrible storm - about 2 times a year. My parents have cable and a Sony rear projection LCos tv like myself and have no pixelation issues except for a dirty DVD. So it is not related to the TV technology - we also have had a Philips LCD TV that had no pixelation.
We have had screen door effect issues playing video games on the Plasma, but not as much on the LCD and not at all on the rear projection LCoS TV.