I also went into marriage assuming that we'd merge all of our accounts together. Because my mother was the "banker" in our family, I assumed my wife would be too.
It didn't take very long for me to realize, however, that she was the "spender" while I was the "saver". I had to set up separate accounts so I could shelter at least some of our funds.
She uses our joint accounts to pay for medical and clothes for herself and the children (and some food and her "mad money"), while I pay for everything else out of a separate account.
She spends everything that gets deposited in the joint checking account, and would regularly bounce checks if it weren't "protected" by VISA card. I save money for the "big ticket" items (like vacations, college for the kids, retirement).
She's prone to invest in "get rich quick" schemes. I'm a more patient investor.
My point in telling you all this is that the best arrangement for your finances depends on the personalities of the two people involved. I'm sure it's really nice when husband and wife both use similar thought processes when making savings and spending decisions (therefore arriving at decisions that are acceptable to their spouses), but that's not always the case.
Couples need to take stock of the strenghs and weaknesses of each person. It may turn out that it's better (or even necessary) to let one person take overall charge of the finances. Pay attention to your finances; catch problems (like credit card debt) before they grow too large.
I'll also say that a marriage in which the two people continue working (and therefore don't have to change the spending/savings habits they had before marriage) are the "best case" scenarios. It becomes much more difficult if you drop back to a single-income family to raise children.
Good luck.