I think Jetbrains is delivering excellent support for stable and widely used frameworks, like JUnit. I think, however, that JUnit support can even be improved greatly, by making it easier to create tests for methods.
If you look at the unitTest plugin, which seems a bit dead at the moment, and has some 'issues' (crashes, code formatting, wrong imports, etc), it's really helpful. It adds an icon to an untested method (a bit annoying that my test methods are called 'testShouldValidateCorrectly, instead of testValidateXXX.
The ToggleUnitTest is also a good example of a very nice plugin: it allows easy toggling between the test in the actual implementation.
I was hoping for a new assistant, which would create a test automatically without prompting for the name of the test class, the location of the file, and the name of the method, extending from the correct testclass (TestCase, RMockTestCase, EasymockXXX), etc. In short: making a test as simple as possible. For me, it would be a great time saver!