I see a property list under each heading as a way of doing columns,
albeit in a less user friendly way. I can see this being useful
anywhere you have hierarchal data to which you would like to add
structure. Currently, I normally transfer it into a table, but it
would be nice to be able to leave things as a list and still define
some columns. See
http://www.omnigroup.com/images/applications/omnioutliner/features/multicolumn.jpg
Perhaps a property list has the advantage of being easier for the
programmers and being a better way to store the data in a text file,
but I think it would be really sweet if an interface were built on top
of it so that the user saw something similar to the picture above.