Build date 7/11/14 and my yellow was VERY minimal or non-existent, I think my imagination made me see it when it's really not there. My wife and kids saw nothing when I asked them to evaluate the display (without telling them about the "issue").
Mine is 7/2/14 and if I turn on capacitive buttons so the area where the yellow is typically shown to be, crank brightness to 100% and open chrome to a white page and stare at it long enough I might be able to imagine a different color. I also burn my retinas out a I use Auto brightness so the only time it goes to 100% is in direct sunlight.
In all honesty, I do not see it on my phone at all and have done the same experiment with my kids and wife and none have had issues or noticed yellowing.
I use on screen buttons as the capacitive are backward for me as dim as can be anyway.
I grew used to the on screen button layout from my Nexus 5 so I am more comfortable and it's easier for one hand operation to have the back button on the left side of the screen.