Currently we are running over 400 Linux-Workstations for scientific staff distributed all over the campus and the number is still constantly growing, two dedicated computer pools for students with 40 machines and several servers, all equipped with Debian stable. Beyond that, all of the over 28000 campus-wide registered PCs have the ability to run our distribution as a live-system over NFS. On a typical workday about 100 peoples use that feature. Apart from the servers, all computers are integrated in our LDAP-Tree and get their home directories via NFS from a central file server.
Updates are distributed via our own internal mirror. To configure these machines we also run a repository with our own packages, so that the users in the faculties do not have to do any system administration. In the near future our 220-node HPC cluster will also be equipped with our Debian stable-based distribution.
Debian was mainly chosen for its ease of administration and software updates. Its well-tested release policy reduces the amount of updates and guarantees stability. Furthermore lots of free documentation is available which allows insights into the technical details of the system.