Ok so here are my thoughts on the matter... I commented a few days ago, with an LG screen and boldly declared 'I have no IR problems'. So stand by, here's something that doesn't often happen on the internet: I was wrong.
After a few days the IR has developed, and I can now pretty clearly make out the checkerboard on a grey background after running the 'Ultimate IR test' on these forums. So it does totally suck, because of the cost of this machine, and I wouldn't tell anyone they were 'stupid' or 'picky' for taking the machine back to exchange it.
But for all those who have ordered a rMBP and are waiting nervously, here's the thing... You can't see it. At least on my laptop, the IR isn't visible on my usual desktop background (A dark space theme) and its certainly not visible anywhere else from normal application windows etc. I'm a programmer, so i spend the entire day with the Xcode interface open on the screen (Prime for IR problems) but honestly, if i ever do need to minimise it, or switch desktops, there is no visible IR that I can see.
So I guess it comes down to personal preference... If you get an LG screen and it has IR then by all means if it annoys you take it back. But in reality, it's not noticeable for every day usage right now. If it gets worse, I intend to take out Apple Care and take it in for a repair long after they've sorted out all these problems.
Aside, this LG screen is simply the absolute best monitor i have seen. The clarity is second to none (obviously) but also the contrast and brightness levels are superb. The blacks are so black it looks like part of the screen isn't even on, it blends perfectly with the edge of the screen. I am completely in love with this display. In terms of colour reproduction, if it's 100% important to you then just calibrate the display, it produces some pretty reasonable results.
In all, the retina MacBook Pro is hands down the best computer Apple has ever made. Yes, it's a 1st generation product, so there are teething problems. But would i switch from a rMBP to a current generation ordinary MBP? Never in a million years.
Just a collection of my thoughts, happy to answer any questions to potential owners who are concerned about aspects of this machine.
Oh and for the record, it's a 2.6Ghz, 16GB, 512GB SSD Model, custom built for the extra RAM, and I still got an LG (Dispelling any theories that custom builds will ensure a Samsung display)