Up to date as of October 16th, 2015.
As I've outlined in the previous post Drupal 8 core now has 4 core modules to deal with language support. This tidbit will be about the simple language setup features provided by Language module, which is the base for every other language feature.
Language module provides a simple language overview screen. You can reorder existing languages, remove languages (except the site default language, which on the screenshot is English) and add new languages. It is not anymore possible to have enabled and disabled languages on your site. This feature resulted in a confusing mess where some places and permission combinations allowed for the use of disabled languages and it was used as a means to stage certain new content. Just use proven content staging techniques (or unpublished posts) for new language content.