I am using Ubuntu from November 2010. That time the latest was Ubuntu 10.10, so I started with it and moved to LTS versions over the time. I have some experience as a unix admin in the past.
My current work involves with a startup in healthcare IT domain with user friendly, high quality hospital management software for Indian Market and we run Ubuntu top to bottom within company and recommend to customers to keep TCO low. Helped around 20 hospitals to migrate their computers to Ubuntu, that makes around 300+ computers running on Ubuntu and about same number of new users to Ubuntu. That is apart from many of my friends whom I could convince to embrace ubuntu.