I've had my 42" Panasonic plasma for nearly two years, and have no evidence of burn in. We watch about 50% high def 16:9 material, and the rest standard 'TV' in non-stretched 4:3 mode with dark gray bars on the sides (this was a setup option on this model). I can't stand stretched images. With this setup and viewing pattern, burn in isn't an issue. I also second the earlier recommendation of turning down the brightness and calibrating the monitor - better picture and longer life.
I have absolutely no regrets on the quality of the picture, and no desire to upgrade to anything else - - - except a larger plasma! :-)
I have absolutely no regrets on the quality of the picture, and no desire to upgrade to anything else - - - except a larger plasma! :-)