I'm working on an administrator interface--nothing new, it's been done thousands of times before--that will be used by both the IT administrators of an organization as well as some more advanced users of the system.
One capability of the interface is to change the roles (each role has preset permissions that aren't currently customizable) for each user. This can be done individually or to many selected users at once. The issue I'm running up against is that the IT admins that I've tested with made critical mistakes when the interface used to change roles didn't show what roles the user(s) were currently a part of.
Showing current state seems simple enough for one user. However, I've not been able to find a good example of how to show, when many users were selected, that only some are part of a role.
My first design used a tri-state checkbox, but the partial-selected state (I used a dash) was confusing to a lot of people:
Other designs I've messed with either didn't show the current state or didn't work for multiple selected users at once.