I received the Rift 3 days ago and love it. It works great. I have no other problems with it except for described below.
First - left lens have this circle in the middle. It must be from the underside. Maybe it's not polished enough from back side during manufacturing process? I took the picture of it(2 pics below). Right lens does not have this issue and seems clear. It's only on left. Sorry for dust on picture. I only used included microfiber cloth gently to clean rift and I don't have problem with scratches or anything. It's just this ring on left lens from what I've found so far. I can kinda see light refracting on it in games and it looks like brighter spot in middle of my vision in left eye. Most of the time it's not noticeable but sometimes I can notice more glare in this place compared to right eye.
Again - what You see in pictures is not effect of lens flare from camera flash. It's there all the time.
And other issue is this pattern of grey dots visible on black background. It's like a stained pattern. Irregular but not changing from use to use. Much more prominent on left screen and less on right. Always look like this on whole black screen. Sometimes I can see the pattern through the dark images too. But this one seems weird. While it's always visible on whole dark screen, I am not sure if it's visible at other times too.
Easy to check on every black loading screen, on Dead'n'buried or in Bigscreen void. Looks like this (couldn't take a picture of it but it looks like very high ISO but only in parts of the screen like on image I recreated below)
I did not had problems like this on DK2... Maybe the second issue is caused by software(some pixels not turning off)?
But first problem I described seems like a lens defect.
Overall the screen door effect is much better compared to dk2 but the image seems "dirtier" if that's the word meaning anything.
I will wait for maybe getting support reply here. After that I might ask for refund or replacement if Oculus can guarantee that repacement unit will be free of those defects. No bad feelings. Its sale, lots of units produced and shipped. It can happen I guess.