Currently the filter-sharing is something we use a lot. And it works really well.
However, the problem with sharing the filters is that only one person can modify them - and that they can only be shared with one group.
Ultimately, the filters are owned by a user.
What would be nice is if you could save filters at the Project Level - and anyone who is a project administrator can Manage them.
They would be public by nature - ie if you can browse the project, you can see the filters.
I guess they would also be for that project only...