We are a company that installs and administrates Linux boxes. We administrate approximately 200 servers and 15 workstations running Debian. We run Debian on mail servers, file servers, firewalls and application servers. We run PostgreSQL database, OpenLDAP, Exim, Cyrus, Tomcat, Apache, Passenger, Request Tracker, OpenVPN, Ruby On Rails, OpenLDAP and many more.
We choose Debian for it's stability, support — availability of security updates —, great packaging system — we pack most of our software as Debian packages —, and wide range of software packages and libraries that come with Debian.