One of the terms you'll sometimes hear from various Microsoft folk is the term "dogfooding". This is a short form of "eating our own dogfood" which means using our own products for our day-to-day work before we ask our customers to.
One of the teams making heavy use of dogfooding is the Visual Studio Team System team...VSTS is being build with...well, VSTS, of course.
John Lawrence has been posting statistics around the team's dogfooding efforts. Interesting stuff.