Isos 160 is yes by far the most affected.
200 it's there in fact but better
360 gets pretty bad too. (160x2)
the phenomenon starts to decrease in higher isos. It's marginal at 500, absent at 800 and above. This fact has been also described in the link you provided and I confirm it: it tends to disappear when increase the isos but really doesn't completly. What happen is that the added grain is giving an optic ilusion. It's totally unconsitent, unreliable and no general rule can be extracted.
The banding is present in the very crappy QT, but not only, in any viewer, so as in Nuke viewer under any config, so it's recorded by the GH2 and not a QT issue. It is a sensor processing (8bits )badly conceived or technically unacheived. A Beta.
It means that you can say bye bye to isos from 160 to 500 on common conditions, unless you want to take the risk of ruining your footage, and even so, nothing's guarantee.
It is present in any configurations (the factory curves), and adquisition format like motion jpegs or avchd.
THIS LIMITATES QUITE A LOT THE SECURE RANGE OF ACTION OF A CAMERA AND THIS IS NOT OFFICIALLY RECOGNIZED NOR RESOLVED BY PANASONIC AND POTENTIAL BUYERS SHOULD BE AWARE OF THIS PROBLEM
then, what Rainer pointed: THIS CAN, AND HAS HAPPENED TO HIGH-END EQUIPMENT TOO AND IS NOT RESERVED TO THE CONSUMER GEAR IN WICH THE GH2 ENTERS.
Can somebody tells me what the hell is that in those price-range? for ex: http://forum.getdpi.com/forum/medium-format-systems-digital-backs/27729-wide-lens-iq-180-shoot-out-digitar-28xl-versus-digaron-32hr-w.html
More people should be aware that when you read a ww consensus, "the-best-bang-for-the-buck", "the-epic-killer" etc etc...we end getting hypnotized but they are wrong and uncomplete infos on what reveals to be an unreliable-problematic product.
And all the noise and good press made arround this camera is pointless. It's only usable for youtube amateurs or indy filmakers, at their own risk.
This camera has issue with and without the hack. it's not the hack, what does the hack is that it enhance the crapperies, it doesn't create them.
Also, there is another different sort of banding issue with the GH2 that has not to do with this one, an horizontal banding in higher isos within the 2/3 lower part of the footage. It's a very known fact now. Those both issues are PANASONIC RESPONSABILITY imo. Who else?
So we're trapped. to reduce the first banding issue, you have to increase isos, but if you increase too much, you may end to get the other banding issue.
THIS CASE DESERVES A WW COMPLAIN AND PETITION FROM CLIENTS AND OFFICIAL DEMAND TO PANASONIC. but it won't happen
as everybody is busy hacking it to pixel-peeping the hair of the talent whaoo... whaaaaa...oooohhhhhh
I think that those compagnies can peacefully keep going producing unfinished products without being very much disturbed by their busy clients.
NOTA: the GH2 is a 8 bit camera, the issue described may be softened by recording to an external device like the Ninja. But there is no guarantee that this issue can be solved nor easy to do.
See a note in Marvels film
and see how tedius the process is: http://marvelsfilm.wordpress.com/2011/04/19/panny-gh2-hdmi-recorder-bingo/
see the DNxHD 175 in a .mov wrapper.
You want to go into this? I don't.
Bottom line: this is not serious equipment and it should be avoided.