I'm always curious since I was faced with this prospect and thought I could do it (Lutheran Protestant > Judaism), went to classes for three months, but finally couldn't go through with it, as I felt I was lying to myself and couldn't live with my conscience. But I'm always amazed when, in my circle of friends, I hear of someone who is willing to go through circumcision or some other emormous sacrifice, like dis-ownage by family, to be with the person they love. (This includes Catholics who marry non-Catholics and vice-versa, who seem to be conscience-stricken as well, in many instances. At least in my experience)