floridman, I feel your pain and frustration.
To be frank, approximately a week ago I got my iMac retina unit. I waited probably two or three days to open the package, due to my busy work schedule. once I finally got around to opening it, I plugged it in and the first thing I noticed was the backlight bleeding issue that you're experiencing. Although my bleeding issue wasn't nearly as bad as yours, I figured it might just be normal for the screen to look like that while it's black. During normal use, the backlight spots are not an issue at all. The only time I would actually see them was when the display would go dark during gameplay, or while watching a video. Like you, I became extremely frustrated because I spent over $3000 on this computer. So I took it upon myself to go to a local Apple Store, and I started playing with one of their iMac retina units. While at the Apple Store, I restarted ther unit several times to see if I could see the back light while the screen was dark. Sure enough, their screen looked immaculate. At this point I was pretty frustrated, so I drove home and the first thing I did was call Apple Care. Their support line was very helpful, and they told me, because I'm in my 14 day period, I can return it for a new one. I got to give them one thing, got another unit on its way, and I should have it in a couple of days. Hopefully, through the grace of God, this new unit has no issues.
One last thing, I believe your issue might be the construction of the unit more so than the screen. I noticed by pushing on the borders of my screen, the bleeding would kind of disappear and reappear. Or, the screen could be bad...Wasn't too sure...
Hopefully all works well for you bud, and Merry Christmas!