Now I'd like to make some points about security. I think you should in any case use Kerberos 5 with Coda, because the default internal authentication is so poor. You need to guard your file servers, since they are by far the most vulnerable point in the cell. And there are potential security holes because most of Coda has not been the subject of serious security testing. Despite this, I suspect that Coda may be more secure than NFS, and certainly not substantially less secure than AFS or DFS, bearing in mind its inadequate encryption.
The Coda developers are well aware of the limitations of Coda's encryption, and intend to replace it with something more serious.