How do I update a Drupal distribution to a newer version? I am looking at using http://drupal.org/project/commons , but I am not sure how easy it is to update a distribution when a new version comes out.

Also, can I use drush to do it, or do I have to manually download and unpack the distribution?
With drush for commons 7.x you can do:

drush up drupal -y
drush dl commons -y
drush updatedb -y