Right out the box, I used CNet's recommendation for my ST50's settings, tweaking brightness, contrast, chroma and hue with my WoW disc (the changes were extremely slight.)
Then I ran the first 100 hours with regular full-screen movie and video game content (try Dead Space, a phenomenal game that conveniently has no static images during play).
My picture is incredibly beautiful and I've experienced zero retention. If this ever changes, then I promise that I'll report back to this thread immediately.
(Enjoy your damn TVs already.)