I spent ten years in one marriage that might have survived had I heeded my inner voice to leave the island when he wanted to go after a particularly traumatic event.
Then a disastrous foray into a hellish marriage with a sociopath that I am still trying to pick up the pieces from....If it's the right one, it is great for many of the reasons cited here.
I have been lucky to find man who has stuck with me during a particularly rough stretch during which things could have gone the other way. As I get older, I realize the paper gives you security in being taken care of when the spouse dies and their family doesn't run you off while they take all the material possessions you accrued together. It happened to a close friend of mine a few months ago, when he tied intestate and his mother, who professed to love her common-law daughter-in-law for 11 years kicked her out of their house and would only let her take her personal possessions. Makes you reconsider marriage so as not end up a bag lady.
Having said that, there people who will fuck it up whether married or not. Depends on the level of commitment and open, honest communication, and a willingness to accept each others' less than perfect qualities as long as the glue holding you together is stronger than the differences between you.
That is all.