Should a couple ever "stay together for the kids"?

If a couple is no longer happy together, should they stay together just to keep their kids happy? Keep in mind both aspects of the arguement:

If the parents are unhappy together, there will probably be a lot of fighting and uncomfortable tension in the home.

If the parents get divorced, it will have a huge impact on the kids, who will probably never be able to spend time with both parents together again. Depending on how old the kids are, it could even lead to severe depression or emotional problems later in life.