I'm using it in one for adults (2.3.2) and have a couple of issues:
First of all, I'm getting the same problem with the block not displaying anything (just "No Users"). I'm an Administrator rather than a Teacher on the course in question, could that be it?
Secondly, I have users with iPads (using the MyMobile theme which I've set up as this Moodle's theme to display to tablets) who can't complete the checklist. They can tick the boxes, but the progress bar doesn't move and, when they click the [Save] button below the checklist and return to the main course page, their checks aren't saved...
I don't have an iPad myself so can't reproduce this... any ideas?