I was trying to use DigitalColor Meter to find the color of a pixel on my retina MacBook Pro, but I found that it was impossible to get the color that I wanted because the smallest that I could move the mouse by was two pixels (in either direction). If you zoom in using the control-scroll trick and disable pixel antialiasing (in the Accessibility preferences), you'll also see that this is the case.
Is it possible to move the mouse by just one pixel on a retina display? It seems like the ability to do so would make the mouse movement smoother. I guess to solve my color problem, I could just take a screenshot and zoom in on that, but it's a lot of extra work.