[CentOS] Single sign-on for CentOS-6

Does anyone here use a Samba4 setup for single sign-on for MS_Win workstations and CentOS-6 boxes? Does anyone here use it for imap and/or smtp authentication? We are experimenting with replacing our existing Microsoft domain controllers with Samba4 based controllers and are contemplating moving all authentication for all our systems, Microsoft and CentOS based, over to Samba when, or if, this replacement successfully completes.

Does anyone have any references for using CentOS with Samba domain controllers that they can recommend? I have found some but the few I have found tend to be Samba3 specific.