Some thoughts about this new document, upon a first, fast reading:
The reasoning and the language are clear and simple. John Paul's works always seemed to have a rich abstruseness and density of reasoning that made one take them in small bites in order to get the gist. Benedict's work so far is much more in the "Latin" or "Roman" way of thinking--logical, gradually building, aimed more evidently at communication rather than meditation. To me this is the most evident contrast between the current pontiff and his predecessor, visible in his shorter messages and now in the encyclical letter.
Benedict seems to have a love for the Classical world and its wisdom. This reflects the sense of many of the Church Fathers that the core of Classical philosophy was the second way by which the world was prepared to receive the Christian message. The way of reason has a universal appeal that may prove (once again, we may hope) to be an effective outreach to the world. No one can say it's too obscure, too "Catholic" (in a pejorative sense, as a sort of closed club whose thinking doesn't compel belief from the secular minds out there). Is it St. Justin Martyr who said that Christianity is "the true philosophy"?
He really boils the heart of the Gospel down to a kernel of belief: "God is love." The opening paragraphs are breathtaking in their directness.
The paragraphs on the Church's duties of love toward the world, love built on justice, emphasize direct action and help. It's not the Church's duty to wait until the government does something to help the poor, suffering and hurt. The Church doesn't exist to build a "utopia" of material good, but rather to help the poor, starting with the poorest. Government's job is to create the conditions where these works of justice may flourish. The Church's political theory is to be the model of love and the first to get its hands busy with the works of love. All else follows, including political advocacy. I think Pope John Paul, Dorothy Day and Peter Maurin would concur. And as the saints' lives testify, this work itself is plenty controversial.