My husband (non-practicing cradle Protestant) and I (definitely practicing cradle Catholic-revert) have a pretty strong marriage. We’ve been married for a little more than four years now, and while we’ve had a few ups and downs, we’ve gone through a couple of “make or break” marriage issues and have come out on the other side as a stronger couple.
I think part of why faith hasn’t been an issue is because I presented it as a non-negotiable from the get-go. He knew that I came with Catholicism, a package deal, that we would be married in a Catholic church by a priest, and that if we were blessed with children, they would be baptized and raised in the Catholic church. He agreed to all of this and while he hasn’t converted (and doesn’t show much inclination to do so), he has developed a healthy respect for the Church and enjoys associating with the priests and other parishoners at our parish. He’s always been very supportive of my faith practices, never stands in the way when I want to go to Mass (he doesn’t always go), Confession, or something at church. He’s very happy not to use any form of birth control, sides with the Church on the issue of abortion, and agrees that IVF would be wrong and a waste of money that could be better spent on adoption (a hot topic as one of our “make or break” issues is ongoing infertility).
I don’t know how well this arrangement would work if the non-Catholic spouse treated Catholicism derisively, or if he or she was very involved in his or her Protestant church. I would think it would be much more difficult.