Hi Lisa, I never had it done for my babies because I would never terminate my pregnancy so it seemed rather pointless.
That said, I was tempted so that I could have a peek at my bubbas.
Even if you did get the test they need to do amnio to confirm which carries a risk of miscarriage. So if you got the test but then decided against amnio it's possible that you could carry a burden of worry during your pregnancy that you wouldn't have had without the test.
As Melanie has said, there's no "right" answer - only one that's right for you. I hope that hearing some other people's opinions helps you make a desicion that you're happy with