I have read the first encyclical closely now; and it's clearly some of Benedict's finest work. I've posted a few of extracts - his critique of Christianity's tendency to abhor the body, his understanding of the limits of politics, his connection between eros and agape - that strike me as particularly eloquent. I'm still saddened by the absence of philia in the document, although one reader suggests that that's a function of Benedict's belief that true philia is impossible for Christians among non-Christians. Here's my correspondent's elaboration of Ratzinger's earlier work, "The Meaning of Christian Brotherhood," in this regard:
"Now, this does not mean that one should be cruel toward non-Christians. On the contrary, Christians are obligated toward their non-Christian fellows in a three-fold manner. First, there's 'missionary activity.' Second, there is agape, which has two forms: a) 'the relations of Christians among one another should have an attractive and exemplary force,' and b) to 'follow the work of the Lord who performed his work of love for those who neither knew nor loved him (see Rom 5:6), directing their love to all those who need them, without asking for thanks or a response.' And finally, the "last and highest mission of the Christian in relation to non-believers is to suffer for them and in their place as the Master did.' (pp. 81-83)
At any rate, I suspect that Benedict's decision not to speak of philia has to do with the fact understanding it contains a harsh truth: that there are insurmountable difference between Christians and non-Christians (and even Catholics and non-Catholics). For what seem to me altogether sensible political reasons, I think Benedict chose not to emphasize the somewhat exclusive quality of the Church."
That helps. Benedict's aversion to Aquinas also helps explain the absence of philia from the encyclical.