I really like the ability in 10.0 to turn on and off certain tool categories and specific tools within a category to keep your toolbar clean.
What would really take it to the next level is allowing users to manage them like bookmarks in a broswer - let me create new custom groups and add anything to them, or move tools among groups.
The favorites method lays the foundation for this, but is limited in that everthing is on one group. Using the method I suggest, users could basically have groups of tools tailored to specific analytic tasks.