I don't like how marriage equality is being increasingly framed as a gay and lesbian issue. It's also a transgender issue, and it benefits heterosexual couples.
My wife and I, while being lesbian, are also transgender, were married on Dec. 30, 2013. Marriages in which one or both persons is transgender have been subject to interpretation by the judge or clerk. Because someone who transitions has a sex they were born with and a gender they transitioned to, the gender of the person is frequently and discriminatorily ruled to be one which puts the couple in a same-sex relationship, and hence not entitled to services. Marriage equality takes gender out of the equation and rules in the favor of love and commitment.
Heterosexual couples benefit because there is no longer a default dominant gender in the relationship, and are free to explore the dynamic that feels more natural to them.