You raise a valid point and I have a solution in mind to try out later this week.  Adding “Anonymous” as a metagroup should be a fairly simple matter.  To avoid inflicting much struggle and liability on myself and others, I'll limit anon role assignments to roles that have no edit capabilities.

Would you see any advantage to also defining a “Logged In” metagroup?

Before the initial release back in May, Role Scoper did provide role assignment for the generic anon and logged user.  But I wasn't happy with the implementation so I took it out.  The metagroup layer is the right place to slide this in.

I think this will help Role Scoper give a friendlier first impression to some users (as well as ongoing convenience), so thanks for the feedback.

For now, you can of course get default hiding by marking each post private and then assign the “WP Subscriber”, “WP Contributor” and “WP Author” metagroup a Private Post Reader role for sections of your choice.

I decided to handle this (and similar feature requests) via Default Restrictions, Default Roles and Default Groups instead.  Note that "Exclusive Roles" are now called "Restrictions"

In your case, you can:

1. Set a default Category Restriction on the "Post Reader" role.  This will restrict the role for all current and future categories, unless a manual unrestriction is set per-category.
2. Define a User Group "Post Readers", and add all existing users to it
3. From the Groups admin page, click "Default Groups" and set "Post Readers" as a default group
4. Assign the "Post Reader" Category Role to the "Post Readers" group for all existing categories.
5. Assign the "Post Reader" Category Role to the "Post Readers" group as a default for new categories.

This could be done via [WP role] metagroups instead, but using explicit user assignment to a default groups allow you to later remove the role from a specific user.  It also simplifies the category role assignment interface.

Remember that version 1.0.0, which brings these features, is still in beta and should not be trusted to a production site.