Most of the couples I know who are my age have the three account system.

Once the basics and essentials like mortgage, food, expenses etc are covered in the Joint account, "his" money and "her" money generally makes things easier when it comes to the luxeries and how each of them wants to spend their own money. It's usually a bit more fluid than that, but that is the general principle. You would do two tax returns as well I'd imagine.

I think it's pretty common in this day and age of two income families.