This plugin Block is in many ways the Block that 'Progress bar should have aways been - in that it ties in directly to the core 'completion tracking' of activities within Moodle
It's possibly one of the most useful Blocks around, and I wouldn't be surprised to see this Block, or a direct derivative of the code, in core Moodle one day.
It is important to understand that there are configuration settings that only the Moodle site administrator can make once this Block in installed, so it will be important for Moodle admin and academic staff to work together to ensure that the global settings are the most appropriate for the specific site and use.
You can try this Block yourself for real on our public plugins site: http://plugins.moodlebites.com