I have one day left on my exchange and I just noticed an odd discoloration on the trackpad. It looks like a stain right in the middle of the pad. You do not notice it direct light- but if you tilt the machine it's clearly there. It almost like a worn spot that might appear on the trackpad after years of use- but this thing is only a week and half old. Could Mac be using refurb parts? Is this worth the hassle of an exchange?