OpenFiler doesn't let you manage users via the GUI. If you want to do any user management like adding/deleting then you must do it via the command line.
It does this because it is designed to connect to an external LDAP or AD server.
Finally got working on my file server, and it turns out that this isn't true, at least any more. While it doesn't look like it, there is an LDAP server built into OpenFiler. In order to enable it, you have to click on the "Use Local LDAP Server" checkbox, and then the bindDN and bindPassword fields set those options for the server in addition to the client. And then you can use the web interface to create groups and users.
I was having some problems early on, but it seems to be going pretty smoothly now. I'll be testing speed tonight and then testing it again running under VMware and under Xen.