Plasma sets have also improved also in quality. Don't ever think that because LCD may be improving, that Plasma is staying static in regards of improvement.
LCD's do suffer from burn-in as Crabby pointed out below. Also, LCD's have poor black level which is vitally important when it comes to rich colors or even accurate color reprensentation.Ever seen a LCD advertise brightness? LCD's also do not handle motion even near to what a Plasma can do and this even goes for the newer 120hz sets. LCD's suffer in viewing arc compared to PLasma. I don't know why you said they were superior. LCD's show SD video very poorly compared to Plasma.
On Plasma, they do have burn-burn just like LCD but like LCD, in most cases, it can be remedied by alternating white and black on the screen. Yes, you are correct, Plasmas do poor at high altitudes.You might have a problem in Denver or something but most people don't live at high altitude. Plasmas have superior black levels compared to LCD and this gives it excellent contrast ratio which is important for color reprensentation.
I bought a Samsung A650 series 50" Plasma. My mother has a Samsung 46" LCD TV. She was nearly floored by the PQ of my Plasma with default factory settings. It made her have second thoughts about her's. She even made the comment that she wished she would of got a TV like mine. My TV doesn't suffer from glare. I even shined a flashlight at it and didn't reflect the light. The picture is phenomenal to say the least. The only TV's that performed better, and I did my research, were the Pioneed Elite Kuros in PQ. I would recommend this TV to anyone.
With that said, who cares about Vizio? If someone says, "Vizio", quality just doesn't come to mind. You get what you pay for though.
Crabby, thanks for pushing me over the edge about the Kuro's. Even though there is a big difference between Elite and non elite brands, I just could never justify the Elite price so I began to research what was the next best thing. Panasonic and Samsung where mentioned; however, the Samsung was recommended over the Panasonic by many users on the AVS Forum.