So up until the latest version of the DirSync tool (at the time of this writing version 6862.0000), in order to force a sync, we first had launch a Windows Powershell 2.0 console on the respective server and then navigate to “C:\Program Files\Microsoft Online Directory Sync” or “C:\Program Files\Windows Azure Directory Sync” folder (depending on version in use) and from here run the “DirSyncConfigshell.psc1” script followed by running the actual "Start-OnlineCoexistenceSync" cmdlet that initiates the sync itself.
With version 6862.0000, we still use the "Start-OnlineCoexistenceSync" cmdlet to initiate the actual sync. However, in order to run this cmdlet, instead of executing the “DirSyncConfigshell.psc1” script, we must use one of the following methods:
Open Windows PowerShell and use the "Import-Modules.ps1" script which is located in the "DirSync" sub-folder.
Open Windows PowerShell and then run “Import-Module Dirsync”.
A small but nonetheless important change to be aware of. Especially if you have and identity management solution that includes logic that force a sync after a new user has been provisioned/updated/etc.
Thanks to Brian Reid for the tip about method 2!