@lilikoi There is good an bad legally. If we can assume both people are good, honest people, legally you are protected financially in many ways. If one of the people are bad news, you could get entangled in their debts being married. So, like I said there is good and bad depending.
If one of the people dies, the other has rights of survivorship, so there is no taxes to pay the way I understand it. If I died, and my longtime live in boyfriend was willed my money, he would have to pay taxes for the money changing hands, but in marriage he owns the money the same as I do (this might be even more important if there are children, because you would want your children taken care of, and not a bunch of your money going to the taxman. If he was dying, God forbid, and only family is supposed to have knowledge of his condition, to make medical decisions, and to be able to be with him in a hospital room, being his legal spouse I have these rights.
If your name is not on the deed of your primary home, most states protect the spouse, even if they do not “own it” on paper, they do have rights of ownership. So, if my house was in my husband’s name, he dies, and wills it to his mistress I never heard of, she doesn’t just get it, not all of it, I have rights as a spouse living there legally, no matter what a f**khead he is. They cannot just throw me out of my domocile. Also, most states it is hard for a spouse to sell property without both spouses signing.