The latest version of Azure AD Connect (1.1.484.0 available at http://go.microsoft.com/fwlink/?LinkId=615771) now supports managed service account to connect/synchronize your Active Directory.
NOTE to take advantage of this new feature you need to perform a clean install; you can not upgrade your existing instance.
When using the custom installation mode, you need to first create the managed service account using the PowerShell command New-ADServiceAccount
New-ADServiceAccount –Name <service account name> -Path "CN=Managed Service Accounts,DC=<domain>,DC=<extension>" –DNSHostName <FQDN Azure AD Connect server> –PrincipalsAllowedToRetrieveManagedPassword <Azure AD Connect server>$ (do not forget to end the server name with the $ sign)
Don’t forget when using a managed service account you need to end with $ (like domain\managedaccount$)