I have recently upgraded to 5.0.4 and decided to attempt to get the whole Zimbra/Samba/SSO thing going as well. I have followed the WIKI instructions and gotten things working nicely with one small exception. I initially did not have any password syncing between Samba and Zimbra - changing either the Zimbra password through the UI or changing the Windows password through Ctrl-Alt-Dlt would throw the passwords out of sync. I installed the sambaPassword extension, and now changing the password in Zimbra preferences does change the Windows login, but changing Windows login through Ctrl-Alt-Dlt doesn't change Zimbra login. It looks like this is actually the easier piece to get working, as it looks like just having "ldap passwd sync = yes" in smb.conf "should" accomplish this, but is not working for me.
Install is 5.0.4 OSS on CentOS 5. smb.conf is pretty much a straight copy from WIKI tweaked for my needs.
Spigot Networks, Inc.