Last time, Samba 4 was unable to operate Group Policies, now I tested a few, and they work! The screenshot below is no proof, but I get a kick out of it ;-)
In this screenshot, you see a fully patched Windows 2003 server in a Samba 4 domain, in its own OU, together with the user 'brel', having applied the GPO setting "remove Search from Start Menu".

The future is free!