Alright. Here's the skinny on the concerns you've got (don't take my word for it. Ask any of the guys and gals here, go to AVS forums and ask the pros there).
Burn-in - I am a VERY careful man. I babied my Pioneer for the first 60-90 days (all programming and inputs set to full screen to avoid pillarboxing or letter boxing, set on movie mode, and varying up my content.) If my sons played a few hours of Mario Kart on the Wii, I'd play some full-screen TV content to help make sure the GUI didn't become persistent. I've not had the first minute's issue with any sort of image retention. We abuse the set now, with no concerns. The precautions we took were worth it.
Brightness - Only an issue if you're putting the TV in the brightest room in the house, AND if the times you're watching produce reflection on the TV. Then, I'd consider an LED-LCD.
Reflection - One great thing about tier-one PDPs like the Panasonic is that they've got anti-glare filters on the glass that really do help minimize reflections. Top-tier LED-LCDs do not. Those sets, paradoxically, have a higher-reflective screen than plasmas now. The trade-off is the higher brightness on the LED-LCD.
Make sense?