We run ours as one account.  Wife tried working when the kids were little.  She didn't last long.  Had to pay a sitter, she did have insurance, but it just wasn't working out as her job was about an hour away and was special education aid with kids with severe problems.  A lot of times she would come home in a bad mood so we decided it was best she quit.  Now that the kids are in school, well, one is half day preK, wife went back to work in a neighboring district as a regular special ed teacher.  She's only about 25 minutes from home now, better pay, better benefits, and better kids.  She now comes home in a great mood, she has a lot of fun with the kids she's with now.  Better pay, closer to home, and she's normally off when our kids our, although their schedules vary slightly being two different districts.

Besides the farm account, we keep a joint checking and a joint savings account.  Normally keep enough in checking to pay the bills, her check gets auto deposited into the savings, and her car payment automatically comes out of that.  So I guess you could say she pays for her own car, but I pay for everything else, including what's left of her school loans.  Some months we have extra bills, and we pull out of savings to cover it, and other months there's a surplus from what I put in our checking and it gets transferred to savings.