I don't mean in the sense that it's more important that same sex couples should be able to go about their lives unmolested than that they should get their marriages recognized by the state. That's undoubtedly true; Sarah from Not You, The Other One puts it very well (quoted, because her commenting system doesn't allow direct linking):
Gay marriage means fuck all when the vast majority of society would rather we didn't exist at all. I'd rather the homos living in a bubble in Brighton sharpened up and campaigned against, eg, Homophobic stuff in crappy newspapers, stronger penalties against gay-bashers, for education in secondary schools, and to get homos included in equal-opportunity employment laws. Really, in the big scheme of equality, Marriage is so not top of my list.
Nevertheless, however much I agree with the sentiment, in terms of whether I add my name to the SSM cause, it's a non-argument.
My point is, I'm not sure it wouldn't be more worthwhile to campaign for recognition of serious relationships that are not marriage, rather than trying to redefine all relationships as marriage.
A campaign for the interplay between church and state to be sorted out properly (both in this country and the US; different problems, but they're aspects of the same category of problem), that I could get myself behind. Access to IVF and adoption services, legal recognition of financial interdependence in all kinds of situations, all that kind of thing, should not depend on trying to shoehorn one's relationship into a particular cultural and religious setup called marriage. Gay people would benefit from reforms in these kinds of areas as much as all kinds of queer people and people whose relationships are frowned on for reasons other than sleeping arrangements or gender.
You'd need a heart of stone not to be moved by the sight of two little old lesbians finally getting to formalize their 50-year relationship. The trouble is, I think in this sort of politics, sometimes stone hearts can be quite an asset. And actually, it's rather disturbing to talk about a marriage between two people who have been essentially married for half a century. I don't feel like dismissing all the hard work that must have gone into maintaining that relationship, and of course all the prejudice and annoyance they'd have had to fight on top of that, because it wasn't marriage and is therefore meaningless.
Also, because I don't like slogans. They either end up not saying what you actually mean, or being reduced to total truisms. Various people have picked up the problems with the original 'marriage is love' tagline; in particular, much kudos to redbird for one of the most marvelous and eloquently expressed pieces of pedantry I've come across! Thank you, Redbird, that really brightened my day.
Of all the variants that people have devised, the one that most appeals to me is Asexual reproduction is love (originally via angelsk, but various others have picked it up). Because the internet needs more cell biology jokes...