The linked CNS article goes into some interesting detail about Ratzinger's own understanding of his work and how this will be reflected in the Herder series:
"When, after some hesitation, I decided to take on the project of the publication of my collected works, it was clear to me that the priorities of the (Second Vatican) Council were the most important, which is why liturgy had to be first," the pope wrote.
The first volume, containing his work on the liturgy, was apparently presented yesterday in Regensburg. The second volume will be out in March 2009, and will feature Ratzinger's postdoctoral dissertation on Bonaventure's theology of history (I recently blogged about its reprinting in English translation through Ignatius). I'm not sure whether this volume will include the original manuscript of the dissertation that was eventually dropped by Ratzinger, but in general the series will make available a number of lectures and sermons not previously published.
This will be a welcome set for any theological library. With the enormous amount of secondary literature being generated on Ratzinger over the last few years, he is quickly moving towards being recognized with Balthasar, De Lubac, Rahner, and others as one of the truly great thinkers of 20th century Catholicism, and in particular a guiding light of postconciliar thought.