Married for 13 years.
Finances completely merged - one shared bank account, one shared credit card. House and cars in both our names. Individual retirement savings accounts.
For us, it's a matter of 'two can live as cheaply as one' - and we take the long view of how we contribute to the relationship. Not everything can be assessed in financial terms. I have never earned as much as DH, and right now I've been out of paid work for 10 years, raising and homeschooling the kiddos, and concentrating on the 'saving money by spending time' part of the equation. My MSc in biochemistry was doomed to be a low-earner compared to his BTech in CompSci :)
(But even when you consider financial implications, when you have preschoolers and have to pay childcare, returning to work doesn't always mean an increase in net income.)
It's funny cos from the outside we look like a traditional conservative set-up, but if the incomes had been reversed we'd have seriously considered DH being the stay at home parent.
Basically, for us it's teamwork. And we sink or swim together. For those who have been through messy divorces that perhaps seems hopelessly naive, but both our parents were still together (until my mother died), so we know at least two ways it can be done. :) We're both good mates who can joke and laugh together, which seems like a good sign, anyway.