When we first started living together, my wife and I would both contribute equally to a joint account for our split bills then keep the rest to ourselves. As time went on, we got married, bought a house, sold the house, bought another, had kids etc. it all gets kinda mixed together. The solution there is I have my own account for like 10% of my paychecks, and the rest goes into our joint account. She gets the same. That way I've got plenty of "play money" or whatever that I don't need to account for.
For us, this is a good compromise. I've come home with game consoles and stereo equipment or gone out to with my buddies and whatever and it's never a question of "how does that fit in the budget?" because it never hits the budget. When I get a raise, my play money gets a raise. It's a good system IMO, and nobody's getting "financially cheated on" (though according to this article I've been guilty of that sometimes in the past too).