The kapabilities package has problems. The listbox on the left contains descriptions for services, but items like "Set up Video4Linux" are too vague. The kapabilities program modifies PAM configuration files, and spews the contents of files it saves to the terminal when doing so. When the "Apply" button is pressed, the configuration for the selected service is saved, but nothing else is, and the GUI doesn't give any indication of this.
Also the user & group lists should have labels saying which one is which. Surely one can figure it out but it's not "obvious" as each user has their own group too. GUI-issues aside the ability to configure capabilities is a *very* nice addition!
You get a more detailed description ("Allow users to set up Video4Linux (allows watching TV on the screen, if you have the right hardware)" on the upper-right. The debug spewage is fixed in 1.0.0-3. I've replaced the Apply button with separate Apply All and Apply Current buttons in 1.0.0-3. Labels for the Users and Groups listboxes are a good idea in general, but it's too late for this change ATM.
Why is it too late? The package is not translated.