I received my first one a few days ago. I had been researching for a long time for a 50" plasma for sports/movies/main living room watching. I wanted plasma because of the better value for the size and to see what all the hype of plasma is about (only had LCDs in the past).
My choices came down between Panasonic and Samsung plasmas. Panasonic's (ST/GT) 2011 series and Samsung's D550/6500/7000. I ultimately chose Panasonic because Samsung's screens were a bit more reflective and their models either hit below, or above what I really needed/wanted...albeit Samsung's were probably more competitively priced. However, I chose the Panasonic 50ST30 because I got lucky and happened to check Amazon when they dropped the price by $100, had a Avatar + 2 pair of glasses promotion, AND had a $150 gift card promotion which made this particular purchase unbeatable. Otherwise would have definitely got one of the Samsung's as I've read of virtually zero issues with them.
Anyway, I read about the horrendous fluctuating brightness problem and I watched some Youtube videos on it but I couldn't really gauge the severity or exact problem and didn't really understand it so I took the gamble. Immediately upon turning it on, I checked the settings and it was defaulted to "Standard" with all levels of picture being at "50". So, the fiance put on "Say Yes to the Dress". Good grief, fluctuating brightness EVERYWHERE, it was insane. It was like watching 2 different TVs and if the TV was confused on what picture mode to go on. I was peeved hardcore. This particular show has TONS of whites in it so I figured that wasn't helping. Additionally the TV hadn't been run more than 10 minutes. My first reaction was to immediately return it, but I didn't want to go through the hassel. So I decided to do a few tests. I tried different picture modes other than "standard" and immediately noticed the fluctuating brightness virtually went away. However, these settings had increased brightness and color levels and I didn't want to push the TV that high in its early few hours of use, so I decided to leave it on "standard" in low brightness to see what would happen. Surprisingly, the fluctuating brightness has drastically gone down as the TV is slowly burning/settling in. I'm around the 20 hour or so mark and I don't see it anymore, if at all **Crosses fingers**. I'm going to be keeping a CLOSE eye on this especially after I reach the 150 hour mark and turn this baby up to high brightness and color. I don't understand how Panasonic could put TV's into production with issues like this though. Their vendors/distributors are going through tons of returns because of this issue so hopefully they will do something about it (maybe a firmware update can fix it completely?).
In short, my suggestion is to weather the storm for a few viewing hours and see if the TV settles in. It seems mine has, but I will be keeping a good eye on it...especially as my window to return gets closer. If I did return, I would look for a good deal on the Samsung's to eliminate any headache. Keep in mind though, the ST30 beats Samsung's PQ up to the 6500 that I've seen. But then again I've read people going lower and getting the D550 and doing crazy calibrations bringing it up near the 7000 levels (with other annoying side affects though).
Good luck on your TV, maybe you just receive a bad one. I haven't tested mine for this "Green hue" problem. I don't notice any issues with my picture quality. After reading about D-Nice's calibration I realized it was worthless and caused nothing but unnecessary apprehension and stress. Watching the TV in lower modes for a longer period does the same thing. But if you are wanting to calibrate it as fast as possible, go with his 100 hour slide show cycle and use his TV settings obviously.