Just as an update, it doesn't bother me at all anymore. The "New Apple Product" phase is over and I'm just enjoying this great device without being hypersensitive to minor imperfections.
Absolutely love the mini and I use it much more than I ever used my ipad 3.
The more yellow portion of your display is not darker. Backlight uniformity is fine.I doubt its a backlight issue being on the bottom and not just random problems with the display. I have a darker (or more yellow) portion on the bottom (home button side)