I just got my new Addi Lace Short interchangeable set last week.
Loving them. It's so nice when I'm working on baby/toddler things that I can change the cable to a shorter length without having to change needles.
I have had one of the cables come loose while knitting, but think it was the way I was holding the needle. I think I was accidently pushing on the area where the needle and cord connect and since that is how you disconnect the cord it was doing what it was supposed to, just not when it was supposed to.
Now that I am aware of that I haven't had any more problems with the needles.