I build Review Board (http://www.reviewboard.org), a code review tool, and its SaaS counterpart, RBCommons (https://rbcommons.com/). We use our public Review Board server for every change going into Review Board itself, and RBCommons for every change going into RBCommons.
While "eating your own dogfood" doesn't work in every industry or product (as some of the top comments are discussing), I'm a firm believer that if you're developing something intended for a typical person (developer, casual user, what have you) to use every day, you really should be using it every day as well. I've used too many products that were "mature" yet felt so poorly designed and developed that you'd have to wonder if anyone at the company ever touched them beyond basic testing.
I work at one of the biggest tech companies and ReviewBoard is our primary CR tool. I generally really like it and don't miss GitHub PRs nearly as much as I expected :)
While "eating your own dogfood" doesn't work in every industry or product (as some of the top comments are discussing), I'm a firm believer that if you're developing something intended for a typical person (developer, casual user, what have you) to use every day, you really should be using it every day as well. I've used too many products that were "mature" yet felt so poorly designed and developed that you'd have to wonder if anyone at the company ever touched them beyond basic testing.