We have two servers: A Samba domain controller running Debian etch to manage six desktop Windows machines and two laptops. This server shares two laser printers. The server runs a incremental (daily) and full backup (every Saturday). The other server runs a shared ADSL connection, where it acts as firewall, DNS, and DHCP server.
We use Debian in Bm2i's network because of its stability and security, and a good secured remote administration. In fact the administrator doesn't work at the business premises.