George Weigel on yesterday's CDF document:
"There is ABSOLUTELY NOTHING NEW in this document. Anyone who thinks otherwise is a theological illiterate who equates ecumenism with political correctness. Period."
And from (non-Catholic) Rod Dreher, this:
The pope is not saying that Protestants aren't Christians, or that people can't be saved unless they're Catholic. What he is saying is that the fullness of truth exists only in the Catholic Church -- that the rest of us have only part of the whole truth. I disagree, of course, but the Pope is right to say that. Secondly, he explains how for Catholics, the word "church" has a precise theological meaning. You can't have a church, in a historical and theological sense, without a valid Eucharist, and you can't have a valid Eucharist without a valid sacramental priesthood ... which you can't have without unbroken apostolic succession.
The pope is not denying the existence of the ecclesial communities of Protestantism, and he's not even denying that Christ's salvific work can be done through those communities. He's only clarifying what Catholicism teaches that a church, and the Church, is. As a former Catholic, I welcome this teaching, even as I disagree with parts of it. There is nothing to fear from clarifying our terms, and in fact a lot to fear from wanting to elide over what divides us, or even deny it, for the sake of ecumenism.
This is not meant to be a primer on the letter, which you can read here - nor is it a commentary, which I'm sure you'll be able to get from better sources than I. This is merely to make sure you're not stampeded by the undoubtedly misleading stories coming from the media, or that you aren't put on the defensive by friends or acquaintances. The best thing to do is read it for yourself, but do so with a confidence to be gained from knowing that this is nothing new or earthshattering, merely a (necessary) restatement of conventional Church teaching.