My wife's N8 has fairly obvious screen burn. Mine, purchased at the same time, at launch, has none.
I keep my brightness on auto, and set fairly low. I also hit the power button to shut the screen off when I'm done looking at my phone and am setting it down (to save battery power).
My wife has her brightness set higher, and always just sets her phone down leaving the display on. We both had our screen timeouts set for 10 minutes to keep them from shutting down while we were using them. But after seeing her bad burn, I've set them both for 1 munute.
It would bug me, but when I showed her how her screen was burned, she didn't care. That's probably a better attitude. It doesn't affect usability, it's just cosmetic, I guess. But it is a shame to have such an expensive gadget look less than perfect after such a short time.
Regardless, it's clear that using higher brightness settings and leaving the display on a lot does burn the screens of these phones. Samsung should provide default screen-saver behaviour, especially at high brightness settings or when longer periods of inactivity are detected. Or at the least, they should warn that this display technology is subject to burn, just as we all knew CRT displays were.
LCDs have spoiled us over the years by NOT burning. With these OLEDs, we have to get used to screen burn again, I guess.