Yes a covenant marriage is a good idea, because the people involved have to take their marriage more seriously. People who enter into a covenant marriage invest time in premarital counseling before they get married. They are less likely to want to get divorced from something that they have invested so much time in.
I believe that covenant marriages are unnecessary because if people love each other, they will stay together. Limiting the reasons that someone could get out of a marriage, just hurts one or both of the parties involved. It could be very detrimental to a partner who is having a difficult time staying with the person that they are married to if things don't work out between them. Sometimes, it really is best to walk away from a relationship that is unhealthy.