There are two areas where uncertainty about your marital status could create serious complications for you: taxes and divorce.
Taxes. On the tax front, your tax return will ask whether you are single or married. Now that the Department of the Treasury has ruled that the IRS will recognize all same-sex married couples for purposes of federal tax benefits, regardless of where they live, federal tax returns for same-sex married folks just got a whole lot easier.
If you are legally married, you will list your federal tax filing status as "married filing jointly" or "married filing separate." Even if you move to a non-recognition state, you will still be married for federal tax purposes. To learn more about this decision, see The IRS Will Recognize All Same Sex Marriages.
However, the IRS has made it clear that this ruling does not apply to same-sex couples in civil unions or domestic partnerships. These couples often face complex tax issues, for example, they may receive state, but not federal recognition of their union.
And for same-sex married couples living in non-recognition states, they will be treated as single for state tax purposes, but listed as married on their federal tax returns.
Obviously, using two different tax filing statuses can create complications, so it's best to meet with a CPA that is familiar with tax issues specific to same-sex couples.
Divorce. For couples breaking up who want to obtain a divorce or dissolution, your legal situation could get sticky. If you married in a marriage-equality state, but you currently live in a DOMA or nonrecognition state, you may have a problem getting your local court to take "jurisdiction" over your case -- meaning the court may say it doesn't have the power to divorce you because in the state's eyes, you're not married. And you can't just get a divorce in the state where you got married, because those states have residency requirements such that at least one of you would have to establish residency (meaning live there) in order to get a court to grant your divorce.
It's worth giving it a try in your home state. If you go into court with an uncontested divorce -- so that you're not asking the court to resolve any disputes -- you may find a sympathetic judge who will grant the divorce. If not, you could try for an annulment of your marriage on the grounds that it wasn't legally valid in your home state. If neither strategy works, one of you may need to relocate temporarily to the state in which you got married, in order to qualify for a divorce there.
Your safest course of action if you don't live in a marriage state is not to get married right now. Tempting as it is to travel to the East Coast or Iowa to establish a legal bond, unless you're adventurous and not at all averse to taking risks, you might want to wait until the legal rules are straightened out.
If you are the adventurous type, at least create a written agreement covering issues of marital money and property. That way, if your relationship does end, you won't have disputes over how to divide your assets. You can find such an agreement in A Legal Guide for Lesbian & Gay Couples, by Denis Clifford, Frederick Hertz, and Emily Doskow (Nolo).
And if you're considering tying the knot out of state, an hour with a local attorney who understands LGBT legal issues would be a great investment. One good place to find an LGBT lawyer is Nolo's Lawyer Directory, where you can search the family law attorney listings for an attorney in your geographic area.
For a comprehensive, easy-to-understand and up-to-date guide to the past, present, and future of same-sex relationships in America, see Making It Legal: A Guide to Same-Sex Marriage, Domestic Partnerships & Civil Unions, by Frederick Hertz and Emily Doskow (Nolo).