I definitely have mild banding in certain room light+background combinations but it seems lie everyone has some. I want my purchase to be as perfect as anyone and I don't want banding either... but it seems like seeking out a certain wallpaper and shutting myself in a dark room is like doing gymnastics to make it visible.
As long as I don't see it in everyday use, I'm gonna try not to worry with it and try to enjoy my phone. It really is fantastic overall (I don't have any WiFi issues, my battery life is 17 hours, etc, etc. If I exchange it, I may clear up the light banding but may not be so lucky with the other issues)