There has historically been an issue in which text vertically or center aligned via
position: absolute; left: 50%; transform: translateX(-50%);
, position: absolute; top: 50%; transform: translateY(-50%);
, or position: absolute; left: 50%; top: 50%; transform: translate(-50%, -50%);
resulted in text that was rendered blurry on devices with a pixel ratio of 1. This would be seen when the positioning context containing element is an odd pixel value in the width and/or height (depending on vertical or horizontal centering), resulting in a fractional pixel value for the positioned element's top or left (again, depending on the axis for centering).
It seems that this behavior has been improved in recent browser releases. Specifically I am seeing the following on a Macbook running OS X 10.10.5: