My case pertains to the Flex Slider particularly as I have not noticed issues elsewhere in the theme.
On retina devices the background image sprite used for prev/next navigation does not account for the 2x device resolution. In the custom css I just referenced the individual images instead of the sprite for now:
 ———————-
 .flexslider .flex-direction-nav li a.flex-prev {
 background:url(‘WEBSITE/wp-content/themes/vantage/images/sprites/gallery-prev.png’) no-repeat;
 }
 .flexslider .flex-direction-nav li a.flex-next {
 background:url(‘WEBSITE/wp-content/themes/vantage/images/sprites/gallery-next.png’) no-repeat;
 }
 ———————-
 Great theme – my client loves it.

Hi Chris. I’ve seen this too. Thanks very much for sharing your fix with us, I’ll log this formally as a bug now. Much appreciated.