Wow, this thread has been quite a read. My condolences to everyone who has had a rough time of it.
Since this seems to be a fairly poorly represented view (that of the happily married, pre-nup-less) I'll share my own situation. I'm sure some of you will consider me hopelessly naive.. and maybe I am. Things seem to be going well so far though, and what else can you really say with certainty?
DH and I have been married for a couple years now, but we dated for nine years prior to this. I recommend this wholeheartedly - I really know the guy, and he knows me. We are the best of friends, and are admittedly lucky that we grew together, not apart, particularly since we started dated when we were so young.
We've both taken turns supporting the other, mostly while going to school. We're now DINKs, and plan to keep it that way, which I would say is a huge advantage - nothing wrong with having kids if you want to, but not having to deal with the stress/decisions/financial strain/energy drain that comes along with that gives you more resources to put towards your relationship and the life you're building together.
We were dirt poor pretty much up until last year when the whole post-secondary schooling thing was done with, so we've lived through that together, and neither of us brought much by way of assets with us to the party. We technically have separate accounts, but I manage our finances so I've always had access to his. I try to keep him in the loop, and he's involved in any major decisions, but mostly he's not terribly interested, and trusts me to handle things. Fortunately for him, I am worthy of that trust.
We talk frequently about our goals and values, and stay very much on the same page. If for some reason we ever did split up, existing assets would be split 50/50. Neither of us has really given anything up for the other's benefit career wise, so alimony would not be an issue. Our pay is pretty similar right now, and if one of us ended up making more, good for them for succeeding in that - no reason why the other should benefit from that outside of a relationship.
All that being said, I definitely understand the cynicism coming from many of you. Call me cocky, but I don't see great chances for long term success for many of the other couples I know, and I think many of them should be concerned about the sorts of things that have been brought up here. I just don't think it applies to me ;)