Drupal 8.6.0 is here. What is different compared to 8.5.6?
There are updated versions of jQuery and Ckeditor.
One of the code changes is to replace a simple Drupal function with a method of an object returned from a static method of a Drupal class. This is supposed to provide some sort of backward compatibility with old code but requires a change to your code.
Layout Builder and Media have major changes. The Media module also gets a companion named Media library with the description "Enhances the media list with additional features to easier find and use existing media items". The Migrate module gets the companion Migrate Drupal multilingual.
There is a new Workspaces module. The description says "Provides the ability to have multiple workspaces on a single site to facilitate things like full-site preview and content staging". What happened to parallel testing? Workspaces sounds like it is aimed at content changes, not code changes or theme changes. Your content editors could experiment with layout builder in a second workspace before messing up the public facing Web site.
For me, the big change is the work towards making media management effective. Drupal 8.5 was supposed to implement all the media management from the Drupal Lightning distribution. Delivery of the last important bits slipped to Drupal 8.6. I am about to upgrade some sites to 8.6 and test the media management improvements. Hopefully it works reliably across all Web browsers.
Drupal 8.6.0 is definitely worth the upgrade when you have images, video, any type of media on your Web site.