I know, I know. I'm actually surprised at how much this thread has distanced from the original question. All I was looking for was a few more online display tests!
I was plagued with a shimmering and almost invisible text when scrolling web pages in like yahoo or even macrumors in my MBA. It had an LG Panel. Got another one and its a Samsung and no terrible flickering. All LCD screens flicker when scrolling and its normal,but not to the extent of the text vanishing. Indicates very slow response time. So that's one test you might want to do.
http://www.marco.org/rmbp-irtest.html
The above is for image retention test. Honestly I don't know, if you can go by that. It could be the screen or persistence of vision of our eyes. Other readers here who are into electronics engineering or experienced in the TV/display industry can enlighten us.
I just opened my brand new rMBP and it has an LG screen as well. But no issues and came calibrated perfect from the factory. I say this because, being the top of the line notebook, Apple probably has more QC on the line for rMBP.
I was initially a little miffed at the LG Panel, but that's because I been reading too much stuff here at Macrumors. But then I calmed down and looked at it objectively without any prejudice and I saw that it was a great Panel. No light leaks,uneven lighting or any tint anywhere on the screen. It was flat as a piece of A4 paper.
After that I am enjoying the Retina display and discovering how things look on this notebook and its a visual feast
Just look for the usual suspects and carefully watch the gray screen when booting, good time to check for uneven light or bleeding.
Try a visually rich web page in various resolutions and if it scales properly without any glitches or flicker etc.
Yahoo doesn't scroll smoothly, but other sites do. It's not a issue with the MBP but of the site.
Check the basic stuff and if it checks out pack it back and enjoy the thing. You have 30 days time to return it during this season I think. Not sure, but check with them.
Remember, if you go looking for something wrong, more often than not, you will find it. I wish it worked that way for money