Researching and planning for a large CIFS filesystem rollout on RHEL has led me to the following presentation.  It steps you through using Kerberos to authenticate CIFS, the issues you will have, and generally spells out CIFS’s limitations on the *NIX platform.

Video: https://access.redhat.com/knowledge/videos/player?videoId=013

PDF: http://www.redhat.com/promo/summit/2010/presentations/summit/in-the-weeds/wed/jlayton-310-interoperability/jlayton_summit_2010-Final.pdf