I had them done with my first and plan to have it done again with this one. My husband and I decided to do it, because if there is an issue, we would like to know about it in advance. We would never terminate, just to be prepared, and have the appropriate specialists on hand once the baby arrives.
But just to prepare you though, we did have a false alarm with my first. During initial testing they said that it was very likely she had a neural tube defect. We went through with the NT scan, but no CVS or amnio (too much risk for the baby). The scan showed a lower chance of the defect, but they could not give us a reason why the bloodwork showed such a high chance and said it was possible that the defect was just not detectable on the NT scan. So I was nervous throughout a large portion of my pregnancy, for what turned out to be a false alarm. When she arrived, she was perfect and is now a happy, healthy 15 month old. So if you do opt for it, please be prepared to handle a potential uncertainty. It does not happen often, my case was pretty rare, but it CAN happen and you need to be able to handle that uncertainty. I obviously think it's worth it, as I will elect to have it done again, I just want people to understand that sometimes you don't come out of it with a definite answer and that can be unsettling.