When building your code, there can be quite a bit of extra information that you are interested in. For example, you might run EMMA on your code in order to log code coverage. With properties, you can save this information, and even look at the history of a property (by way of an exported spreadsheet).
Usage: As a developer, I want to save the average cyclomatic complexity of a function (pulled from JavaNCSS).
For this example, we're going to take the information out of "target/javancss/javancss_metrics_util.xml"