WD40 or silicon (plumbers' grease?) - re: Creaking Issue
I'm an old (somewhat old - @ 65, one stops counting) PC fellow. I have interest in the so-called "creaking issue" of the MBPr (or rMBP), as I am contemplating buying one.
As I understand it, poster Nik came up with an oil resolution. If indeed this works, then perhaps WD40 or liquid silicon would be a better alternative. And if I understand the issue correctly, a very (very) small amount of either on certain screw heads and ground clips, etc., will solve the noise issue, which apparenty is caused by thermal expansion at certain joints. This is likely why Apple in its wisdom decided to leave some room for such expansion. And we know that the metal-to-metal (or other materials) rubbing noise "should not" be an Apple customer's concern.
If one goes this route: How to apply WD40 or other aerosol lubricants? The best way is to use a tooth pick held far away from the MBPr, spray the lubricant on the pick, and use it as a tiny dropper on each screw head, clip, etc. Perhaps plumbers' grease (very tiny amount, fellows and gals) would be better, as its viscosity is higher and will withstand some heat.
Having written this, I am not a big proponent of monkeying around with a new MBPr - I would not do this. I believe the best solution in this case would be to return it within the return time window - however, (smile) I can only imagine Apple or a third party vendor recycling these MBPr's to re-sell to the same people having this same problem.
In my case, since portability is not a major concern, perhaps an iMac would be better. Good luck, everyone.