Interesting nugget from the munki-dev list, a description of how to stop the auto-login that occurs after FileVault 2 unlock (I haven't tested this yet). You essentially disable the credential forwarding from the disk unlock window to the login window.
Find the "system.login.console" array.
Find the "mechanisms" array within this.
Remove the line "builtin:forward-login,privileged".
Save and reboot.