See last link for the details about the following highlights:
- Added new generate command. based on the focused DCG project, which ships with 50ish generators for scaffolding all the things in Drupal.
- Improve table wrapping
- Remove Finder+Launcher. Relying now on a site local Drush (see install docs)
- All classes now follow PSR2 code style standard.
- Formalize the API for Contrib to offer Drush commands and generators. See devel and devel_generate modules for an example.
- Changes since 9.0.0-beta1.