Apart from using Debian in various internal projects (mysql server, knowledge base, document server, etc. etc.) we are currently packaging a stand-alone file server to be used with our flagship product.
Debian has allowed us to break from using RH (ew) by providing a minimalistic, simple distro that we can configure ourselves without needing a bully GUI or X-Server running - although the desktop implementations of Gnome and KDE are nice. We also appreciate the testing process that Debian takes into account (we use Sarge primarily but Sid on some personal systems) and know that what we get in Sarge is pretty stable to begin with.