I have some thoughts on this, and may comment more extensively in the future. In brief, I have been concerned that the three primary offenses/moratoria identified by the Windsor Report (“moratorium on the election and consent to the consecration of any candidate to the episcopate who is living in a same gender union”, the “moratorium on all such public Rites [of Blessing of same sex unions]”, and the “moratorium on any further [cross-provincial] interventions”) have been unduly viewed as equally upsetting to church unity. In fact, the first two offenses have made the third necessary as an unfortunate and temporary recourse. Williams recognizes, however, that no absolute equivalence of faults should be interpreted from his statements:
...when a province through its formal decision-making bodies or its House of Bishops as a body declines to accept requests or advice from the consultative organs of the Communion, it is very hard (as noted in my letter to the Communion last year after the General Convention of TEC) to see how members of that province can be placed in positions where they are required to represent the Communion as a whole. This affects both our ecumenical dialogues, where our partners (as they often say to us) need to know who it is they are talking to, and our internal faith-and-order related groups.
I am therefore proposing that, while these tensions remain unresolved, members of such provinces – provinces that have formally, through their Synod or House of Bishops, adopted policies that breach any of the moratoria requested by the Instruments of Communion and recently reaffirmed by the Standing Committee and the Inter-Anglican Standing Commission on Unity, Faith and Order (IASCUFO) – should not be participants in the ecumenical dialogues in which the Communion is formally engaged. I am further proposing that members of such provinces serving on IASCUFO should for the time being have the status only of consultants rather than full members. This is simply to confirm what the Communion as a whole has come to regard as the acceptable limits of diversity in its practice. It does not alter what has been said earlier by the Primates’ Meeting about the nature of the moratoria: the request for restraint does not necessarily imply that the issues involved are of equal weight but recognises that they are ‘central factors placing strains on our common life’, in the words of the Primates in 2007. Particular provinces will be contacted about the outworking of this in the near future.
Members of ACNA, AMiA, and other renewal movements seem to be provided space for making their case, although the continued reality of consequences for their actions remains. I think that this is appropriate, and that a spirit of repentance should pervade the Anglican work that is currently going on in North America. I do not believe it is appropriate to call our work "schismatic", but it has certainly proceeded against the requests of global Anglican bodies, and I don't think that we need to be afraid of affirming this tragedy and taking responsibility for it, even as we affirm the Gospel work that is being accomplished in it.
One reason why I take the cross-provincial ministry to be appropriate is because it is reactive to a situation of disunity, and it stands as a temporary effort with the goal of moving towards further unity in the Gospel. This also leads to a consideration of the fact that offending provinces will be restricted from the official ecumenical dialogue of the Communion. In a conversation with Tony Hunt and Mike Dagle on this, I mentioned the fact that, really, ecumenical dialogue has already been stalled for years because of the Anglican crisis. The ARCIC suspended dialogue with the Anglican Communion soon after Robinson's consecration, in order for the Communion to sort out necessary discipline issues. The Russian Orthodox Church has made explicit statements about its willingness to work specifically with "the members of the Episcopal Church in the USA who clearly declared their loyalty to the moral teaching of the Holy Gospel and the Ancient Undivided Church." And as the ACNA has taken shape, other communions have indeed retained ecumenical connection with these Anglicans apart from official Anglican Communion channels. In many ways, it seems that all of the provisions Rowan Williams now offers for ecumenical bodies has long since been, more or less, common practice. This leaves out consideration of ecumenical discussion with other Protestant denominations,* of course, but my rather limited sense is that these sorts of talks go on at a number of different levels, and global Anglican policy for official ecumenical dialogue will not especially impede other ongoing engagements.
All that said, this seems to be an important development as the Anglican Communion continues through the process of discernment and discipline. The next moves will come (less importantly) from the global reaction to the letter and (more importantly) from the Anglican governing bodies as they incorporate this call into future policy.
*I am not one of those people who feel the need to distinguish Anglicanism from Protestantism. We are as Protestant as the Evangelical Free Church, regardless of incense, apostolic succession, or whatever else distinguishes us. We are also perfectly "Catholic", as are all Christians baptized into and adherent of the faith.