We come across them all the time when doing internal network pentests (most organizations use AD for managing their fleet of end-user systems), and occasionally

We come across them all the time when doing internal network pentests (most organizations use AD for managing their fleet of end-user systems), and occasionally external tests as well. Stackoverflow is a site that comes to mind as being known for running their production systems on Windows Server. It's useful to have experienced, but I do take issue with exclusively (or primarily) focusing on one ecosystem as a mostly-publicly-funded school.