I have worked a bit with the configuration options for matrix-based security and think that it would be useful to be able to set all or no options for a given user entry with a single checkmark. This will mean that you can easily verify that you have set all options correctly for an admin user (or removed all for anonymous user).

e.g.
username O O O O all ( ) none
Anonymous O O O O ( ) all none
somebody ( ) ( ) O all O none

maybe with the inactive options grayed out

with javascript, that should be easy to do while the user clicks