To me flickering happens when I open recent apps on the launcher or when I ve a popup (inside the application, on internet etc.) with a dark trasparent effect under. The same graphical problem turn up heavily with the youtube application or sometime using keyboard.
It's very very annoying this problem. It doesn't limit the use of the tablet, which is very fast and smooth, but simply ruins something which, simply, would be perfect without it.
It will be interesting create a class action, a mail, with the signature of who wants a resolution of this problem, to send to Sony for forcing it to realize a solution.