I shake my head sometimes reading posts in this forum. Someone actually went through 8 iMacs?! Man, Apple support employees are a patient bunch. If I was the owner of a business, I would be furious over costumers like that. Computers with real defects should obviously be replaced, and we should all demand better technology in future products, but...
First off all, all iMacs will have some glow, esp. in the corners, that's the IPS technology. All iMacs will produce a certain degree of yellow/orange hue in the lower half, which is related to viewing angles (again IPS limitation). The fact that the late 2012 iMac screen has an overall slightly warmer hue is a good thing! I have to use f.lux on my older MacBook Pro and MacBook Air because they have screens with a harsh, blue-ish hue, which is hard on the eyes.
Jeez!