Separate. Just worked out that way. I mean I thought it would be a good idea. We moved in together and kept separate finances. Even after we got married, it just seemed to proceed that way. She had a job, direct deposit, and paid some of her own bills. I already had my "stuff" set up. I am in the financial services industry and have been around these discussions for a long time.
Even if your finances are joint -- there are things you can to. There are very structured and simple steps that you can take to protect yourself and your finances, assets, and more. There is so much potential for massive problems here, so you must protect yourself -- in every way possible.