"Reduce rework", "Hit scheduled release dates", "Improve developer productivity"...

We see these all the time as we work with companies on their process improvement initiatives.  Unfortunately, they all lack specificity and measurability.  Thus, they're both difficult to measure, and make lousy motivators.

Instead, make your goals specific.  TFS can help make the measurement of those goals easier or possible.  For instance, replace "Reduce rework" to "Reduce time spent on bug fixes to 25% of total effort.".  You could also use something such as "Reduce bug count to 15 per Scenario".  Now, even though some scenarios are larger than others, you have an average target you can hit.

Specific values are also motivating.  When you are trying to limit the number of bugs to 15 per scenario, as the number of bugs increases, there is psychological pressure (and motivation) to ensure that further scenario development is conducted more carefully (possibly with the introduction of unit testing).