Let me start by saying I'm an audio guy, not a TV guy, so take this for what its worth.
I bought one of these two weeks ago(the 82"). Out of the box, I saw some faint vertical banding on an all white screen, no other color. I made a number of changes to the picture settings which reduced the visibility of the bands to the point where I can't see them even when panning across a white hockey rink, so I'm good with it. I made the changes not to specifically address the banding, just to improve the picture in general. I suspect reducing the backlight a bit and turning off contrast enhancer had the most effect on minimizing the banding but I don't know for sure.
What this all says to me is that you should not have to live with DSE/banding you notice watching regular content. What I would do with a new unit is adjust the picture settings to your taste and go from there. I would not make any return decisions based on something you only see faintly on an all gray/white screen, or test patterns, that is not a problem watching your normal content.