Wow, this is a seriously tough topic. I can chime in from two points of view, as I am pagan, which brings one set of beliefs to the table, and my uncle, who split with his wife shortly before my husband and I split, is a Free Methodist with an entirely different belief system.
In some ways, mine was easier. I simply wasn't given a choice. My husband and I went through a series of stressors one right after the other, so things were difficult, but I assumed it was situational and temporary. Apparently my husband had other ideas, because he simply packed up and left in the middle of the night. No conversation, no explanation other than "I really love you and I'm really sorry," written in a note that he left behind. Despite my best efforts, he simply refused to speak to me, and forbid his family and friends from any contact as well. He called me months later and we arranged a time/place for him to bring back the things of mine he stole that night, and he brought divorce papers as well. I was so shocked, stunned, and out of options that I just signed them. Come to find out months after that, from a mutual friend, that he never actually filed the papers. So he's living with his new girlfriend and refusing to file the papers, and I don't want to file because I feel like he should pay for it. So we've been separated for a year and a half, no hope of reconciliation, and it's looking like not much hope for divorce anytime soon. But the point is, all possibilities were taken away from me, and that's simply the way it was. I have no religious issues to consider with it though, as pagan ceremonies are worded: As long as love shall last, rather than Till Death Do Us Part. Obviously there was no love left, at least on his part. Also, we were only married 2 years and had no kids.
My uncle's situation was completely different. His wife left him once before, when he was struggling with lymphoma. They already had two kids and a house, plus as I mentioned above, are Free Methodist. That church does not allow divorce, as a general rule. She eventually came back around (conveniently enough, after the cancer treatment was over and he was able to go back to work). Well, a couple months before my split, she left him again. No explanations really, other than "I don't want to be tied down." He got her to agree to marriage counseling, they fought, they argued, he tried everything. She served him with papers. He stressed to her repeatedly that if she took it that far, then he was going to go through with it this time. She wouldn't get another chance. She insisted and the divorce moved forward. Meanwhile she was calling him to do things for her, constantly. She was helpless without him. He was also paying three times as much child support as he would with a court order, because he wanted to make sure the kids didn't suffer. He consulted constantly with his preacher, who told him he was absolved, because he couldn't do anything about it.
Finally, after a year of fighting their house was sold and the profits split. Thousands upon thousands of dollars had been spent on lawyers. My uncle finally started dating someone new. THEN his wife wanted him back. She started begging him to come back. He consulted with his preacher, his family, everyone. Everyone including the preacher told him not to go back. She's done it twice now, what's to stop her from doing it again. Well, at this point he decided he had had enough. The divorce went through, and he is now happily married to the new woman, who is everything he deserves. And everyone, from the preacher to the church members to his family, strongly believes that he did the right thing.
So the point of all my rambling is this. Yes, divorce is a horrible thing. No, it shouldn't be undertaken lightly. But no matter what your religion, when your partner completely checks out and is unwilling to attempt resolution, what choice do you have? That's a personal question that everyone must answer for him or herself, but it's a reality that happens all too frequently. And IMHO, you cannot know when going into a marriage that something might happen 5, 10, or even 40 years down the road that might make your partner completely flip. Sad but true.