Hi there,
I've noticed that when I associate Test Cases with requirements for a specific release, those test cases are not considered to be associated with that release (At least not for the purpose of the "Display Data for:[Release]" filter on the TC page). I think it would be useful to add that association to the filter, or even automatically make the Release association as soon as you connect a Test Case to a Requirement with a Release number identified, since every test case on a requirement for a release IS a test case for that release.
This would save the extra step of identifying all the TC's associated with Requirements you are interested in, and updating them individually. Especially since that cannot be done from the TC grid view.