Lets say in this example that I have a cabinet. I want to place a hinge for a door; I am making the hinge a sub-assembly so I can control its configurations of "Open" and "Closed".
My goal is to show the hinge in a closed configuration. If I right-click on any part of the hinge and try to change configurations in 'Component Properties', I get properties for the individual part of the hinge sub-assembly. This means I then have to go chase down the sub-assembly in the tree. (here is a video showing what I am talking about http://screencast.com/t/XDZxCBFh)
The example I am showing is a small one, but applied in a large assembly this will drive someone crazy. I used to run into this a lot when working with air cylinders.
If you need any elaboration let me know.
Solidworks