Drush: Update core from stable to dev I would like to upgrade from drupal core 7.7 to 7.x-dev, is this possible using Drush?

UPDATE:

Ok, looks like either I needed Drush 4.5, or the process of updating Drush from 4.4 corrected something with the installation, as drush up drupal-7.x worked, and I'm noticing that drush up now shows all installed modules everytime.
Yes it is. Navigate to your Drupal directory and run the following command:

drush pm-update drupal-7.x


Note you can use the same tactic to update any module to a development version from a stable version, as well as update a development version to a newer, stable version.