Paged Power
Tag pages and author pages are now split up into multiple pages if there are to many articles for a given tag or author. They also come with their own RSS-, RSSJS- and ATOM-Newsfeed.
Now there is also a browserconfig.xml
and some XMLs to have notifications on Windows 8+ desktops.
Also the templates have been updated, and non-theme templates moved out of the theme template folder, so theme editors might not break them by accident.
There is also improved HTML for Youtube, Vimeo, as well as an all-new Giphy integration.
Under the hood there is a lot of new prototype
going on.