Fedora
Used by 9 peoplefedoraproject.org ↗

“The primary desktop machine is running the Fedora Rawhide distribution.”
Jonathan Corbet Interview, Linux kernel contributor, editor (LWN) · via Uses This 
“Most of them are old Dell boxes running Fedora Linux, and there is a Cisco router.”
Andy Hertzfeld Interview, Developer (Macintosh), software designer (Google+) · via Uses This 
“I work at Red Hat and I'm also the team lead for the Fedora Design Team.”
Máirín Duffy Interview, UI designer, usability tester (Red Hat, Fedora) · via Uses This