Back in 8.04 or so, when PolicyKit was new, we had a GUI "browser" that enabled us to easily decide things like whether a user should be allowed to shutdown the system when other users were logged in and if it should always be allowed or only while on the console, etc.
Then those things suddenly disappeared and though it seems PolicyKit is still in use, I haven't been able to find any similar GUI to actually configure the policies. What happened?
Very little information has been available about the long absence of a policykit gui until it was discussed last year at a session of Ubuntu Developer Summit. It was discussed there in detail, and in that 'blueprints' session discussing desktop authorisation it was indeed noted that there
is currently no simplified utility to customize policies
for policykit. However, an important point arising from the discussion was that
PolicyKit upstream is against something as complex as policykit-1's "Authorizations" window
So it seems this may be one of the problems in implementing such a program.
Nonetheless, it was conceded that the command-line interface available was 'too hard to use' and so while the idea of a policykit gui seems to have been well received, I don't know whether there are any firm intentions to bring back a policykit gui anytime soon; it looks like a wishlist item really.
However, somebody with official connections might be able to give some further useful information on the current situation.