I do. I pretty much have since we have been together, but their marriage has been over a number of years, and she is remarried herself. I think when the exes have moved on into other relationships, it is a lot easier, than when the exes are alone. I think it is just a security issue, really. I do not feel threatened by her, and vice versa, and it also helps if everyone acts like grown ups. I know, sometimes thats hard,lol.
She and I meet halfway when my stepson comes down, we discuss anything he needs to get done such as homework, etc, if he is sick, we discuss meds, pretty much everything.
My fiance also talks to my ex and his gf as well, though my ex is a little more difficult at times, but then again, not as much time has passed since our divorce, and there is still a great deal of bitterness on his part.
I think it takes time and patience to build a good relationship with someone's ex, but I also believe it is something that is VERY important for the children involved. Everyone should be on the same page as far as parenting the children, and at least make an effort to communicate, even if you're never buddy buddy.