I did. My husband and I were separated for a year before our divorce was final so, in our minds, we were officially "broken up" well before the state of Washington said we were. We discussed dating other people before we started dating other people, though, and both agreed it was okay. Of course my ex changed his mind when it became clear that I was dating again, and asked that I not have any sleepovers at "our" house until the papers were final. Of course, he was having sleepovers in his new place, so I felt it was a double standard.
It's very tricky. My main concern was maintaining a good relationship with my exhusband for my son's sake, so I might have held out on the sex if I thought it would've been detrimental to that effort. But we discussed it openly and worked it out.