Drush 3

As root:
aptitude
Find drush under PHP.

At the bottom of the information about the drush package, there's an i that means installed next to 2.0 and a p that means no packages or config files or anything are present next to drush 3.3.

Type + when the drush 3.3 line is highlighted.

Then type g to upgrade (twice, first it takes us to a confirmation page).

Note: On Agaric's servers the package list is updated daily by a cron job, but updating the package list can be invoked by hitting u if necessary.

The version of drush in Debian is way behind. Drush 3.1 has been out for a month, Drush reached stable 3.0 on April 23.

Stefan was unsympathetic:

That does not mean the package is ready. What the upstream authors consider stable and the Debian community considers stable might be different things, too. Quality is Debian's top priority not up to date software. In addition to that it will only get into the next stable distro and maybe into the backports repository. In that case we get the upgrade automatically.