With much love and pride, the Drush maintainers have released Drush 9, our latest version that pairs well with Drupal 8. Some highlights:
Generators
Quickly build a Drupal module, controller, plugin, entity, migration, etc. Drush 9 builds upon the DCG project to offer almost 100 generators via a Drush command.
Modernized config, site aliases, and output formatters
Drush rewrote its config, site alias, and output format systems. These YAML files are easier to read & share. We factored out these subsystems for use by other PHP projects.
Command Authoring
Like Drush itself, the command authoring process has been thoroughly modernized. Start with a generator that scaffolds a class for you, and then add your logic, guided by the file's comments. Drush's new OO APIs are available to you just be extending our base class - DrushCommands. The generator can port commandfiles from prior versions of Drush.
Symfony Powered
Just like Drupal 8, Drush builds upon Symfony where possible. In particular, we replaced a lot of homegrown code with Symfony Console.
Familiar friend
Drush minimized changes to the commands, in order to ease transition to Drush 9. If you know and like sql-sync, pm-enable, and config-import, you'll be able to use those in Drush9 without delay.
Documentation
We recently debuted a www.drush.org marketing site and a new API docs site (powered by Sami). These supplement docs.drush.org and the traditional drush topic system.
Composer oriented
The PHP world hasembraced Composer for dependency management. We bid fond adieu to dl, make, and drush pm-updatecode. Hello world to composer require and composer install If you run the deprecated commands, Drush helpfully suggests a replacement.
Get started
To get started, see our install docs. Especially note we recommend that Drush be a dependency of your Composer project (aka a "site-local" Drush).