Full disclosure: We are coming from trac which has a drop down with checkboxes. I probably first saw trac a decade ago so that makes sense to me but there are probably other ways to accomplish the same thing. http://trac.edgewall.org/query?priority=highest&priority=high&status=assigned&status=new&status=reopened&col=id&col=summary&col=priority&col=status&col=type&col=milestone&col=version&col=severity&col=resolution&order=priority
Use cases:
* Eye-ball a count of something. For example, search for all of the project foo tickets and see 'a lot' are in status X but 'not very many' are in status Y.
* Narrow search before bulk-edit. Search narrow it most of the way, but just click on a the last few tings to bulk edit. Doing that without opening up each ticket requires being able to see whatever field is relevant.