We support the STS because they are the organization of the Evangelical Catholic (read "high-church") element in American Lutheranism. We think it is wise to support the one (to my knowledge) Lutheran organization fostering the understanding that Lutheranism is a variety of Western Catholicism, and of course, to network within that group, politically . . . )
The ECCL Priests who are members of the STS do not believe in the ordination of women under any circumstances until there is a broad "consensus fidelium" across Western Catholic Christianithy - including the Roman Catholic Church that this is proper and Scriptural, and the leadership of the STS knows this.
If the STS ever adopts a formal policy that its members must as an article of faith and a condition of membership, must state either verbally or in writing, that they support the ordination of women "across the board," the Archbishop will order the ECCL Priests who are STS members to leave the STS. And that will be that. But that is not the situation right now.
That said, to support the STS as American Lutheranism's only "high-church" Evangelical Catholic organization we encourage our clergy to join. Personally, I do not belong to the STS. I belong to the OCR (the Order of Corporate Reunion) and the Evangelical Theological Society (ETS;) but I would join the STS as well if I had the time to do participate fully, attend the retreats, etc., but unfortunately, I do not.