Having a 2005, then a 2008, I disagree. That being said, the real story here is that voltages are set to change over time, but according to people at AVS, Panasonic goofed on the algorithm so it jumps too much. The black level it has after the jump is still awesome, its just not as good as when the tv was purchased.
I personally do not think they have a leg to stand on, even though I think Panny screwed up. Lets face it, all tv's lose some sort of PQ as they age, and everyone knows a plasma ages in a certain way, and colors shift badly (at times).
Also, Panny never guaranteed that it would a certain light output at black, so its a hard one to prove.
Maybe I should sue toyota because my transmission does not shift as smoothly at 100k miles as it did at 0. To me this, this is a small band of AVS fellows with meters who are complaining about a black level in a 2009 tv thats still better than the 2008, and anything Samsung offers...
The CR of my LED local dimming set blows stuff outta the water, but that does not translate into real world performance.