I don't know, it seems to me that the relationship may have less conflict when one person (the woman) acquiesces on everything, (submission), and the other (man) is the boss of everything. But happy? How many men are truly happy to have a wife who is just someone to boss around, cook and clean? Yes he's "well-cared-for," but aren't happy marriages the ones where each person contributes to the relationship and partnership, each person is heard and respected, and each person has standing in the relationship to be complete without it, but chooses to stay because that's what they want?
IMO, the marriages (both in the Org and out) that are happy are the ones where the couple has a partnership, not a hierarchy. The JW marriages that work happily (not just "work") are usually the ones that are somewhat in defiance of the entire headship arrangement.
Just my opinion, and how many happy relationships do I know of? A few... certainly less happy ones that I personally know of than miserable ones, or just tolerable ones.