The Wordpress plugins installed in the Vulnerable Machine are not enabled 'out of the box'. In order to get the most out of the tutorial they should be enabled. This is easily done: Login as 'admin/password', select Plugins in the left hand column and click 'enable' found right under the name of the plugin. Then logout and continue enjoying the tutorial.
Personally I find the tutorial most informative - I have already seen quite a few vulnerabilities in the Worpress sites a I manage
PS The above is true both for the version on the DVD and the downloadable version.