Issues around "my money/his money" don't usually come up, although I do admit to the question of who's paying for dinner coming up. A long, long time ago, we went through the exercise of splitting expenses based on each income. Housing (rent or mortgage) has always fallen to me; credit cards, home equity, car pmts, utilities fall on him. And we've adjusted things over the years as incomes changed. He was in school when we got married, so I took the hit for a lot of years. He now makes a lot more than me, so now he pays the lion's share. So we don't really have discussions around anyone's "turn" to pay rent/utilities, etc.
I have two big reasons for separate finances: first, he used to be TERRIBLE at balancing his statement and I was NEUROTIC about it (although with online banking, I haven't balanced anything for years now). Second, my grandparents - they held everything either jointly or in his name. When he died suddenly, ALL of their money was tied up in probate and my grandmother spent months in limbo waiting for the estate to be settled. I never want to be in the position to be denied access to my own money.