Built in revision history and document management makes this ideal for companies without a dedicated document controller, and makes life significantly easier for document controllers who are using paper-based systems.
I've used Confluence as a Quality Management System at several companies; traditional QMS’s need pretty dedicated management by a document controller to make sure revision history is maintained, changes go through an adequate approval process, and only the latest approved versions of documents are being used. Confluence essentially handles all of that, which means companies without the means for a dedicated document controller can still implement a QMS, and/or companies with a document controller benefit from the added efficiencies.
Really speeds up creation and approval of policies and procedures and provides a centralized area for users to access current versions of documents.
Sometimes has issues with cron jobs crashing - need to check more recent versions to see if this has been resolved.
I'd also love to see integrated project management with Gantt charts, but I'm a sucker for Gantt charts.