This is actually a really cool feature. Basically, you can have one large repository to administer instead of lots of smaller ones, and you can treat any subdirectory level as a single repository.

Want to checkout all Apache Software Foundation projects?

    svn checkout http://svn.apache.org/repos/asf/

Want to work on Apache httpd?

    svn checkout http://svn.apache.org/repos/asf/httpd/

Maybe you only care about mod_proxy?

    svn checkout http://svn.apache.org/repos/asf/httpd/httpd/trunk/modules/proxy/

Apache server becomes a subproject of the new Apache MegaOS? Just move /repos/asf/httpd/ to /repos/asf/megaos/httpd.

See also FreeBSD repository: http://svnweb.freebsd.org/base/