Is the light white or purple to your eye? It looks a bit like an IPS white glow, but a bit worse. How far away was that taken from?
If it's visible and it bothers you in normal usage definitely RMA it. If the light is white (as opposed to reddish/purple) then RMA it.
Do dell ship you a new panel if it's literally a few days old or just a refurb?
RMA it to the shop, you will get a brand new one then no?
To be honest that looks pretty average for a Dell U2311H. They don't have good brightness uniformity and frequently suffer from a combination of 'IPS glow' and backlight bleedthrough. This is exaggerated in pictures, without fail - if I took pictures like this of most of the monitors I review people would probably be scared off ever buying them.
That's what I was thinking when I saw the model but IPS glow is firstly purple/red, not white/yellow (which is almost always backlight bleed), and IPS glow isn't visible in room daylight.
. So from that huge sample size of '5' it appears that your U2311H is a bit of a dud, to put it bluntly
.There is a small side-office near where I work with no windows that has a U2311H in it. Since everyone left the main office at 17:00 I've just been in to check what the screen looked like in complete darkness (sorry - didn't have a camera to hand and couldn't do this earlier as it would p**s people off). Overall it looked quite similar to what you are observing in terms of the 'patchiness' but the upper left corner was a lot better. There certainly wasn't that almost fiery white-orange hue to the image. I also checked a larger room with some U2311Hs in but it was too light to get a 'perfect' comparison. Nonetheless I set up 3 of the other U2311Hs with a black screen (connected to bl**dy slow computers - it took a while) and none of them had any corners with bleed-through as severe as your top left. One of them had a noticeable 'patch' on the bottom left but even that was closer to your bottom left than the top left.
P.S. Sorry for referring to it as 'your' - I'm sure you want nothing to do with it once they collect it/replace it. So from that huge sample size of '5' it appears that your U2311H is a bit of a dud, to put it bluntly
.
.Basically, if you are aware of the problem in normal daylight/room light enough that it bothers you, then return it. I have a similar corner glow on my ips monitor but I can only see it on a totally black screen in the dark.
But, as PCM said, make sure they won't just send it back to you and say it's a normal glow.

Much better! And more similar to the U2311Hs I tested in the office.![]()