Hmm. Well personally, I believe that sex isn't all that great without a deep relationship with the person. Y'know? Just sleeping around with every Tom and Betty just doesn't appeal to me.
That being said, if your in a committed relationship then I see nothing wrong with it. What is marriage? A piece of paper? Not saying it isn't something to want later on, but just saying it isn't everything in a relationship.
On a side note and bringing up an interesting side question, as a Gay person I am not allowed to legally marry in many countries. What are the opinions on it then?