It would be great if you were able to re-run tests directly from the test viewer. When I'm working on a test, I jump into the test runner, go and find the class, check it then run the test. If it doesn't pass, I make changes and want to re-run, and I have to go back into the Run Tests window to find the class again.
It would be great if you could either right click or select an individual Test Run from the Test Results viewer and click a button to re-run the test classes that were included in that run.