I had been dating my boyfriend for 2 years before we moved in together; we've now lived together happily for the last year.
Even though my bf comes from a Catholic family, we really felt it was important to strip away all the 'fantasies' we had about marriage and see it for what it was- daily tedious decisions about money, jobs, future, etc, and make sure if we decided to get married it would be based on a realistic understanding of what marriage entails.
Though we live together, we are still quite conservative in many respects- neither of us have lived with anyone before, and by far the most conservative among among our peers when it comes to sex, dating, prior sexual partners, etc.
There are a lot of studies indicated a relationship between people who move in together and high divorce rates. REMEMBER that these are all correlations not causations. It is pretty impossible to tell if the reason for the divorce was that they moved in together. In other words, if those same people did not move in together, would they have gotten divorced? There's no way to tell. There are a lot of reasons for the findings of these surveys- one major explanation is people who move in together are more likely to be liberal, progressive, and less religious. They therefore are more likely to get divorced if they are unhappy, whereas people who are more religious or conservative are more likely to eschew divorce as even an option, even if they are unhappy with the marriage, someone cheats, etc. (please note I am NOT making judgment statements on divorce, living together, etc. Just looking at these studies/findings on correlation from a proper statistical research vantage point).
That said, I recently read a GREAT book I'd highly recommend called The Marriage-Go-Round. The author, an anthropologist, cites one of the reasons that people who live together before marriage are more likely to divorce is that they got married because they had sort of a 'why not' mentality. They moved in together, started living like they were married, and then got married as a natural next step, without talking about it or examining their relationship rigorously. I see this is a useful cautionary example for people who do live together (like myself) to continue to examine the relationship and decide if breaking up or getting married makes the most sense, not just getting married because you're "basically" married already.
Just some rambling thoughts. Whether you live together before marriage or not is completely up to your own situation and what works best for you
