I hear that most people see a problem with "splodges" being seen on the loading screen playing uncharted, I haven't noticed that myself.
So I just made a black .png picture and copied it to my Vita. It looks like the Vita is turned off to me when looking at the pic, I turned off the lights in the room and It isn't giving off a hint of light.
I'm wondering If anyone else, who has noticed this issue, can test this. I'm not sure If I got lucky or this test just doesn't show the OLED flaw.