I am with the majority here. While the tests are in theory relatively safe, they are not COMPLETELY safe, and whether or not that very small risk is worth it depends upon how important the information is to you, and what you would do with it.
I did the blood test screening but neither the CVS or the amnio with either of my pregnancies, and I was 38 and 41, respectively. I would not, under any circumstance have terminated pregnancy, and no other reason could be provided to me for having these tests done. What was interesting was that with my second pregnancy I sensed that doctors actually worry about being sued if your don't take the test and end up with a baby that has Downs. I had to be very clear that I knew exactly what I was doing in declining the tests, and the discussion was repeated during multiple visits.
It's been interesting to discover that a lot of women also decline the blood test screen, because it isn't all that accurate, sometimes indicating a risk of Down's when there really isn't one. For me, the opportunity to be prepared that something might be wrong was worth the risk of bad information, but I would not have taken the CVS or amnio even if the blood test screen had shown high risk.
I am glad that you are asking this question. I think it is important for women to understand why they are offered certain tests, and if the potential uses of the information are consistent with their personal values. The choice is entirely yours, even if the doctors don't always present it that way. You are the only one who can know how much value the information has to you.
Congratulations on your pregnancy and my best wishes for a healthy and happy baby!