This whole topic is still in the "I don't get it" category for me. While I can understand that everybody wants equal rights, I wouldn't saddle anybody with the trappings of marriage law (along with the fine accoutrements of divorce law). A piece of paper that costs you money now and may really cost you later; besides, if a relationship isn't adequate enough without the paperwork, I'm not sure how much the paper adds to it.
The only possible benefit for some that I can think of is where you need the formal marriage to extend health care benefits provided by an employer. Absent that application, any other benefits you can think of? One doesn't need marriage to leave assets to a partner after death.