In the MIT AI lab the
Officially Supported flavor of GNU/Linux
is Debian. There are approximately 100 user workstations running
Debian, as well as a small but growing OpenMosix Cluster serving
The switch to Debian was made official in September 2001. The largest reason being the ease of package management, which users love (users here get that kind of freedom) and also allows the sysadmins to semi-automate security updates (we like to check the updates on a test system before forcing them on the users, but to date there's been no problems).