The individuals have to meet the same requirements as if they were getting married (financial interdependence, etc.)
You guys are both wrong to some extent.
Kurt, the act would apply to all couples, not only same-sex couples. Heterosexual couples who do not wish to get married would be able to benefit from it.
Alex, the act has nothing to do with marriage. It would merely give an American citizen the right to sponsor his/her foreign national partner for permanent residency.