Living together before marriage helps you decide if your partner is the right choice and if you can adapt by his moods, habbits etc. The same goes for him.
I see living before marriage as a trial. Can we understand each other and complete one another during this time? If so, yes, by all means, go ahead and get married.
If not, and there are signs leading you to believe that this is a bad choice, then decide what is the right call for your life.
IMHO, living together before marriage is a must!