Well after a few hours of trying out my replacement phone from Sony the display is good but not perfect. There is the very very slightest tint of yellow at bottom of the display, but it's hardly noticeable, and certainly a big improvement over the 3 previous handsets I had. Also after having been on the internet and playing at least three 20min plus videos on YouTube I could not see any yellow spot appearing. I am still weary, as some users have reported the yellow tint/spot appears after a couple of weeks, but hopefully this wont be the case with mine.
Proud owner of the htc One in black.