Upgraders: Please delete any drush or drush_extras directories in your drupal site. Drush now gets installed outside of web root.
Among the new features :
Drush is completely Drupal version agnostic, allowing you to only need a single Drush installation, per server. Thanks vingborg.
The dl command can now download themes, translations, and install profiles in addition to modules.
Drush now provides the updatedb command, allowing you to run update.php from the command line. This command works for both minor and major version upgrades of all core and contributed modules, across Drupal 5, Drupal 6 and Drupal 7
Added uninstall command for modules.
The drush_extras commands have been rolled back into Drush itself, which provides the same functionality without having to download an optional project.
The help command has been greatly improved, and provides complete documentation on all optional parameters and options that can be passed to the script for that command.