Department of Measurement and Control Technology MRT (Department of Mechanical Engineering), University of Kassel, Germany
We use Debian/stable for our firewall/packet filter, on our department server (Samba file server and domain controller, WWW, NFS, Git) and on numerous desktop computers for software development in C/C++/Python/Maxima/Matlab and for typesetting with LaTeX and LibreOffice.
We chose Debian because of its capabilities for simple maintenance and updating, as well as for its stability.