Personally, I'm on a Debian desktop exclusively since woody. During university years I used it for scientific research. Later I also introduced it at work (the Hungarian NREN). Most of our servers are running Debian by now, thus our various projects required developing different aspects of Debian. Both the GRID project and our current virtualization environment needed extensions to the Debian Installer. Our AAI infrastructure needs started the Shibboleth SP2 packaging effort. Russ Allbery mentored me in team maintenance, until he stepped down recently, providing the primary impetus for my application to Debian.
Meanwhile other projects led me to contribute to the freeipmi packaging, and also to get my first own package (sblim-wbemcli) sponsored into the archive (thanks to Russ Allbery and Bernd Zeimetz). I've also got two other projects already packaged for internal use, which I'd be glad to share with the community (a Pacemaker resource agent for libvirt transient domains and an SQL-based email merger).
Right now my main focus is packaging the contemporary HA stack as a member of the Debian HA project.
Ferenc Wágner