I wonder how many 5D3 owners will actually send their cameras in.
I am most certainly not going to bother - the disadvantage to losing my camera, even if it is only for a day or two far outweighs any conceivable benefit of "fixing" what is a complete non-issue to me.
I do occasionally take photos in a very dark environments - example http://farm5.staticflickr.com/4136/4798974366_4761573c37_b.jpg, where this "issue" would arise.
However, (a) under those circumstances, I do not leave the LCD light on, as reflected light from that could possibly ruin the photo and (b) I do not rely on auto exposure anyhow.
I just cannot imagine any realistic real-world scenario where this "issue" would affect the quality of my potos, so I am just going to happily ignore it and continue enjoying my new camera.
I'm 15mins away from Canon Service Center, Irvine CA.
I have no issues with "LIGHT LEAK ISSUE" - So...no issue no service.