[natesm]

Text on rMBP at "1920x1200": http://i.imgur.com/FAemY.png

I figure that what it does it use the actual rendered pixel grid for subpixel calculations.

[glhaynes]

Is that in a "Retina app"? If so, my understanding is that text for them is rendered by the system at the right size (so not rendered then rescaled) at any resolution.