This is great news for new and existing users of Azure Active Directory Authentication including Office 365, InTune, CRM Online, etc.
This feature simulates Single Sign-On by copying the hash data for user passwords from on-premises Active Directory Domain Services Domain Controllers into the Azure Active Directory Authentication Service. It also updates password data into Azure more frequently than it does other metadata such as DisplayName, etc. DirSync will detect when a user changes their password and attempt to synchronize it within minutes.
If you’re running the legacy 32-bit version of DirSync, you must first uninstall the older version, and then install the newer 64-bit version on a differen computer.