If you have a screen with no problems (an no other problems you can find), and unless this is really annoying you, I would probably just keep it because what happens if you return it and then the replacement has the yellow screen problem?
My trackpad is not perfect. I actually noticed this before I even booted my Macbook Pro for the first time, but since this was my second unit (first Macbook Pro would not charge) I decided that if the screen was perfect, I would keep this one.
My trackpad is not perfect. I actually noticed this before I even booted my Macbook Pro for the first time, but since this was my second unit (first Macbook Pro would not charge) I decided that if the screen was perfect, I would keep this one.