Hi Jim
In order to verify if this is a common problem we need the same examples shot on other cameras. So far we are working on hear say and looking at different types of shots with different content. There is no way we can say where the issue is without comparing eggs for eggs.
It may be that people just don't see the fault due to the shots they are taking. I didn't see it for a couple of months with outdoor shots, moving shots etc.
To prove your point are you able to take a short 5 sec MTS clip on your GH2 of a soft coloured surface or wall under exposed by a few stop and then post it for us to download and try?
Surely this would not explain why CS5 plays our clips fine? There is a diffenrece in the way CS6 and CS5 is handling MTS files. What is that difference? There in is the reason for this problem.