Problem with retina MBP display at low brightness

My new retina MacBook Pro has an issue with the display when brightness is anything below about 55%. It appears that certain areas of the screen don't dim, resulting in a pattern that ends up looking like "stage lights". At first I did actually mistake it for an intended graphical effect, as I first noticed it on the textured gray screen that appears during software update restarts.

Alas, it was not part of the graphics and is always there. When the screen brightness is increased above 55%-ish, it becomes invisible since the rest of the screen is bright enough to match the permanently-bright spots at the bottom.

Here is a photo of the effect in low light with a flat white background:



Note: My rMBP's display manufacturer is Samsung.

I am taking it in to the Apple store tomorrow, but I was wondering if anyone else has seen this defect before. I am curious how common (or rare) it is, as I can't find any discussion of it online so far.

I'm debating between exchanging vs. returning it for a full refund (I am within the no-questions-asked 14 day window), since I got it to replace a 2010 MBP that had a water accident but only has minor issues. (Not sure, now, that the $3K+ upgrade was entirely worth it given that my "older" MBP is still not that old.) Maybe it's better to wait for a second-gen retina MBP before upgrading.