My fiance and I did one, it was absolutely fantastic
We got paired up with an ''experienced'' couple at the end of the course to have some one on one sessions. We were so perfectly matched with this couple meaning that they had gone through similar issues to us. That couple are now coming to our wedding!
What is interesting is that, I only suggested it because my friend had done it with her fiance the previous year....and ended up breaking up with the issues it threw up! (Obviously good that this happened before marriage)
What I was most surprised at was that, we did ours in Feb/March this year and some of the other couples were getting married within a week or two of the course ending!
We are not getting married until October and it was always in the back of my head, well if something totally serious came up, enough to end the relationship, we would at least have time to cancel the wedding!
Luckily nothing did come up, it has only strengthened our bond (I know, massively corny)
Now I would suggest to everyone getting married they need to do the course no matter what, just choose wisely where you do it. Our church is very contemporary and modern - Hillsong esque - so when we mentioned we lived together already no one fainted however at the more old fashioned churches we may have been made to feel like the devil!