TestMatrix has a great feature that allows a user to run a test while in the Visual Studio environment. By right-clicking in a file, on the file, a folder, or using the Test Explorer tool window, a developer can run a unit test and see the color-coded results in the test file (through a highlighting in the left sidebar) or in the test explorer.
What makes it nice is that a user can run a unit test and view the results directly in the open window. I like being able to execute tests at a folder level, because I am often working in a specific folder at one time, working on the code and the tests. Plus, the visualization makes it more clear, and it has an icon that appears in the side that shows the error.
Furthermore, code coverage icons state what code wasn't hit, and what code took the longest to run.
There is a very useful feature in the TestMatrix product, created by Exact Magic. It is the Tear Off Editor feature, which can be invoked by Studio Tools > Tear Off Editor. This feature tears off the window, which can be docked like the properties or solution explorer windows. This means that when you dock that window to the bottom, you can have two code editor windows open at once!
I like to use this to open up a unit test and the code that unit test is working with all at one time. Very great feature!