It would be handy to have a way to union multiple filter's worth of results into one result set. It should then be possible to feed said union into one of the portlets such as "Show Saved Filter" or "Two Dimensional Filter Statistics".
An example user of this would be one of our development managers who wants to track results for users assigned to two seperate development groups (e.g. "Dev-UI" and "Dev-Communication" or something along those lines).
Criticality on this is pretty low but the convenience factor would be extremely high