Apologies for the long post (I feel I should offer a potato).
On Retina resolution screens Blender 2.8 is rendering low-res aliased images in the viewport where it should be rendering crisp high-res images as per 2.7x.
The images below illustrate the issue:
Soft aliased edges in 2.8:
While crisp sharp edges in 2.7:
And it has nothing to do with render / preview settings / samples as they are the same in both files and final renders are fine. I think it's a glitch in the 2.8 Beta version. Can someone report it? Or is there a setting I'm missing?