flatstate2010 saidI think the study is somewhat skewed, at least in my opinion.
First off, this just looked at married couples? So that means they didn't look at gay and lesbian couples that were not married but had some type of commitment to each other.
Also, how long have gays and lesbians been able to marry in the United States? Not really that long when looking at long term data so it would be hard to say that this would be the case over the long term.
I would also like to know if any of these groups have open relationships. Gay subculture is much more willing to tolerate this than a traditional married couple.
You can go ahead and google but from what I recall of studies I've read in the past I believe that even before marriage (and leading up to marriage numerous studies were done naturally in attempts to justify to the hetero world our relationships) most found that our relationships were either as solid or more likely longer lasting than theirs. Which makes sense because we generally know ourselves better, sexually, before entering a relationship. Practice might not make perfect, especially if you keep doing it wrong, but it tends to help you get to know yourself.
As to your slight on open relationships as being something merely tolerated, and therefore not counted as legitimately as a sexually closed relationship, you can go fuck yourself.