I have tried importing an entire site, and I have tried importing the pages, posts, and comments separately. Either way, I get nothing but Failed to import and Invalid post type error messages.
This plugin is a total bust, and there is no support for it, either! Importing content is crucial functionality. Allowing it to be totally broken and doing nothing to respond to bug reports from users is going to drive consultants away from using WordPress for client projects. It will drive us either towards more flexible hosted solutions, like Squarespace and Weebly, or towards other open source content management systems, like Joomla and Drupal.
WordPress really dropped the ball on this one. Is anybody listening?