This is more specialized instance of the inability to filter on multiple values for an axis.
I would like to be able to filter and search for a group I have created in FogBugz 8 (see this post for the difference between groups in 7 and 8). In FogBugz 7, you could filter by group to find cases in projects which were set to a specified group. I would like to filter for cases assigned to users in a specified group.