We are using Debian GNU/Linux on more than 50 servers. They provide a wide range of tasks: Internet sharing, video registration, terminal access, file sharing, virtualization, document workflow, backup of private or important data and many others. Debian's amazing flexibility makes it possible to apply it everywhere we want.
Debian is our choice because it is a very stable, well-known, widespread distribution with a huge community. There are no surprises or unexpected things with Debian administration and support.