On English Wikivoyage Traveller's Pub, User:Andrewssi2 notes
The banner on your test page is very blurry on a Macbook Pro Retina with the Safari browser. The same banner used on Asia looks fine.
"test page" being referred to is http://pagebanner.wmflabs.org/wiki/Roppongi ( This has the new proposed banner template - Blurry )
"Asia page" being referred to is https://en.wikivoyage.org/wiki/Asia ( This has the old Banner template currently in use on Wikivoyage - Works fine )
Banner being used: https://commons.wikimedia.org/wiki/File:Ladakh_banner.jpg
This summarises the support for "srcset" http://caniuse.com/#feat=srcset