Long post incoming.
I myself got married about two years ago, and I figure someone might be interested in my thoughts from "the other side".
This post is concerned with whether marriage itself is a good decision. I'm going to put aside the debates about polygamy and homosexuality and all the other stuff and just talk about what I've experienced. I'm talking as a man in the context of a monogamous heterosexual relationship, so your mileage may vary, but I believe some of the insights are pretty universal.
I didn't believe in marriage for a long time. By "not believing" I mean I didn't see a reason for marriage to exist as a social institution or interpersonal status. I always figured that if I was in a commited relationship with someone, why would I need to bother with vainly bragging to the world that I plan on continuing that committed relationship?
Talking purely from a rational point of view, to an extent that IS true. If you are in a stable long-term relationship, there's no need from a social point of view to get married. After all, you're committed to each other either way.
Of course there are legal benefits involved in marriage--tax changes, visitation rights, simplified estate planning and paperwork involving family and children. Obviously, if you want those benefits, marriage is a good idea.
But marriage also severely limits the amount of independence you have in your life. Two people sharing expenses means that either one of them having a job is now much more important--it's very difficult to go back to school, or to do extensive traveling. Time spent on your hobbies now goes to doing things with, or for, your significant other. There will be fights and hurt feelings. You no longer have total privacy in your home. And if kids come onto the equation, your life (and hers) are now completely devoted to the young'uns. I was told this by every married couple I know, and my experience has corroborated this.
I couldn't comprehend myself ever willingly surrendering all that freedom for the sake of a marriage. I valued myself and loved my independence too much. I couldn't envision trusting someone so much, and wanting so badly to be with someone, that I would want to make such sacrifices to be with her.
My wife and I dated for just under two years before we got married. I had never connected with someone so naturally, so completely. I had never met someone with whom I could so easily be myself and not be scared of rejection, indignation, or mockery. We completed each other and complemented each other in a way that neither of us could really describe. We quickly became each other's confidant, lover, best friend, and place of solace. We craved each other's presence in our lives, and we didn't want anything to come between us.
In the meantime, something changed in me. Something about that attraction and that desire made me want to marry her. It made me want to make a definitive promise to her that I would never harm her, never leave her, never bring her down or make her unhappy. I wanted to show her a tangible expression of that promise; proof that I would follow through, never waver, and keep that commitment for life. I wanted witnesses to know that I was doing this, that we were to give our love to no-one but each other. I wanted to tie our fates together in a way that was very difficult to break, giving us further motive to stay together and work through any of our issues as partners and equals. I wanted to give my life to her.
She felt the same way. So we got married.
In retrospect, the biggest lesson I've learned is this: Marriage is impossible (and pointless) to ponder in a vacuum.
Marriage constitutes a big commitment and a big challenge. Everyone involved experiences profound life changes, and their futures shift in a way that's impossible to comprehend. It locks you into a life no longer fully under your control. Everything about you--your thoughts, your hobbies, your work, your goals and aspirations--is now shared with another.
If you don't have someone with whom you naturally share those things, marriage seems like a terrible idea. And it is. Never, ever marry someone you don't naturally trust, or who doesn't demonstrate that they're worthy of your trust.
But that desire to share has to come first. You have to want to give your partner a big part of yourself, and you have to be able to trust them to take care of it. The love you feel has to drive you to want to merge yourself with them, becoming an inseparable unit that brings wholeness to each of you. It's that level of trust and companionship that makes a long-term relationship worthwhile in the first place.
Search for that wholeness first. When you find it, the decision to marry will make itself.