I've read through it, and find it very wise and encouraging on first reading. Pete Vere says it's a "bombshell for canonists," and I'll take his word for it. More commentary and reaction will likely be coming in all weekend and through early next week; I'll try to add links to this post as they become available, but I have a few more below:
Father Z. on the letter
Damian Thompson at the UK Telegraph predicts the proposed apostolic visitation will be "a grisly affair..."
The hermeneutic of continuity says the media response has been predictable...
Life-after-RC highlights sections of the letter that might cause the Legion to reflect...
[More to come]
In the meantime, if you've read the letter and would like to share your thoughts below, please do so!