We have questions surrounding the repeal of DADT, not the least of which is how open service will affect the rights and benefits of "unioned" gay service members. Much of the complications above — where they are married, marriage versus civil unions, where they are posted — do not matter. The military is part of and subject to federal law when it comes to benefits. So, federal benefits that inure to a married couple are given to couples legally married where one or both service in the military. Those couples may receive benefits from the state in which they live, but they receive those state benefits by virture of their state residence, not by dint of their enlistment.
DOMA blocks the federal government from ever recognizing a state-sanctioned same-sex marriage, which means it prevents the federal government from granting federal benefits to those gay couples who legally married in a marriage equality state. Since the military is a branch of the federal government, the military will be blocked from extending to its gay married couples the benefits it extends to its straight married couples.
The fact that someone is "domestically partnered" or "civilly unioned" does not matter, just like it does not matter for those civilian couples who want federal benefits pursuant to these unions, but cannot get them. As we know from the recent DOMA cases — Gill v. OPM, Massachusetts v. HHS and the more recent cases filed by Lambda Legal and the ACLU – many of the benefits the plaintiff couples want are contingent on marriage, which makes them, as married couples, "similarly situated, but differently treated" under the law. The cases would not be the same if the couples were unioned, but not married.
But, the military could institute a benefits policy that extends certain benefits to non-married, but unioned couples. It could not grant all benefits; some are incumbent upon marriage pursuant to statute. Then again, military retirement works quite differently, with health care, pension, death benefits coming from separate statutory schemes. Any benefit extension would be a privilege over and above those granted to civilian folks, but our service men and women have certain rights and privileges that civilians do not, anyway. The executive branch could sign off on this benefits policy, but an act of Congress — say, a future Defense Reauthorization Bill — could overturn a hypothetical executive order granting some federal benefits to non-married, but "unioned" gay service members. Note that this is all very hypothetical; more possible for the purposes of this discussion, rather then likely under this political climate.
That someone is married in Iowa, but is stationed in Nevada does not matter for the same reason as above — military benefits are federal benefits, denied to gay couples not by dint of where they live, but because of their sexual orientation or the sex of the person they love and married.
So, my conclusion is that there seem to be a lot of questions with simple answers. DADT's repeal does not force the military to give benefits to same-sex married couples. Quite the contrary, DADT's repeal is a step short of full equality because DOMA prevents the military from extending those benefits. The end of DADT simply allows those of us who are openly gay to serve honestly and serve our country with integrity and not hide who we are. Open service does not require the military to recognize its gay relationships any more than, say, Iowa's marriage law requires the federal government to recognize Iowa's gay relationships. According to the US military now, gay service members exist and their intimate behavior is no longer illegal; whether they are married is another matter.
You know what this means, right? On to the next, I say.