On top of what I've mentioned here and here, there are even more cool features on VSTS2010:
- Rich text editor when editing work items
- Test case runner which allows a tester to pull the test case from TFS, follow the steps and flag them as pass/fail. But even better, this is all being recorded as video, so when the bug is sent back to the developer, he can replay the exact steps to reproduce it.
- Creating bugs will also log the exact system information of the machine the tester was running on
- TFS will even log a call stack to allow developers to analyze and reproduce the bug
- Test Impact View: once you do a code change, it will identify which unit tests
- Gated check-ins: no changes are committed into the repository until the change is verified. TFS will queue a build in the build server, will get latest version and it will verify that it is valid before commiting the change.
- UML: VS can now generation sequence for the application's methods, to help analyze the impact of a change
If you haven't upgraded from TFS 2005 to 2008 yet, I'd recommend you do it now. The transition to 2010 will be much easier from 2008 according to the guys in the VSTS team. Also keep in mind that VSTS2010 will only support SQL 2008.