The Economics Department runs Debian on all its servers (there are four main ones), on five workstation-servers that are used by graduate students, and on over 20 workstations in almost all graduate student offices. It is also used by several faculty members, although a few others use Red Hat and most use other operating systems.
In large part, we use Debian for historical reasons. When we first started to use Linux, our local expert was a visiting graduate student who was (and is) a Debian developer. We continue to use it primarily because of the ease of upgrading and the efforts of the Debian security team.