Rolling Up is pretty common in Project It is, for those just joining us, the ability for summary tasks to contain information from the tasks 'under' themselves. This is illustrated in fields like Work or Cost where the value of the summary task field is the sum of the tasks under it. These fields are 'rolled up'.
Project 2007 adds a sibling to rollups: Roll Downs. Rolldowns, though, do not happen between summary and sub tasks but rather between Tasks and Assignments or Resources and Assignments. Rolling down is an attribute of task and resource custom fields. It allows you to specify how Assignments on a task or resource will have it's values defined for a custom field. The default is no rolldown so that an assignment custom field only gets a value if you enter it. Rolldown means that an assignment custom field will have the value of task or resource field.
You used to have to write VBA code to do this.
While this is not earth shattering stuff it is pretty cool, provided you are as geeky as I am about this kind of stuff. :-)
Oh and did I mention that you get as many fields as you want now? 30 Enterprise Project Outline Codes not enough for you? Need 50 or 75? How about 100? OK. More on this later...