We are using Debian on our core servers (5 machines). We chose Debian
because it is stable, easy to configure, easy to maintain and upgrade,
compatible with all major standards, and there are lots of software
available for free. Moreover, we are very concerned about freedom and
privacy, and we know Debian source code is regulary audited. Debian is
nicely designed, it
just works but can be tailored if needed.
Thanks for everything!