Keep in mind that NZ panels are different from those in the States and through out Europe...
My NZ 50" V10 suffered rising blacks just like the US and European counterparts. Its a design flaw and is not region specific.
Your 50V10 is/was now 2 generations behind the current model, time to compare the most recent TV's don't you think?
I was only responding to your initial comment that blacks won't suffer. That isn't proven to be true and regardless of how negligible a rise may be, its important not to talk in absolutes. Everyones expectations are different and what may be invisible or a minor annoyance to one person, may be a dealbreaker for someone else.
TBH, black level rise is the least of my concerns with the 2011 Panasonic plasmas. They have a few other issues that need to be dealt with first. None of which prevent me from recommending the ST30 here, but like all current displays (or tech in general), the new owner needs to decide for themselves what is or isn't objectionable. Buying from an understanding retailer is well advised.