Using the customization buffers, i've just seen one behaviour that seems strange to me:
Withing the buffer [*Customize Group: Killing*], i've changed the value of the "kill ring max" property. Then, if i click with the mouse on the "State" button, I see (among others) the option "set for current session". But if I put the point on that button and push Return, i don't see that option in the [widget-choose-buffer] buffer.