Yes, we went down that road early in our marriage. Hell, we thought it would be fun, but it did cause some issues.
When there are three people in the act at one time, someone is going to get kind of left out. It happens. With a one on one encounter, it's all about you and the partner. With a third person thrown in, things get a little dicey.
After going down this road four or five times in a three week stretch, we sat down and talked about it and decided to eliminate this from our life.
What was weird was the woman we brought in, who was younger - a law student at SMU who had an internship at my wife's firm - started calling us all the time. She would call me at work and my wife and work and offer to come over and make dinner for us and was really pushing the issue. It was like she fell in love with us as a couple.
We could tell she was a little psycho and agreed we wouldn't try anything like this in the future. Look, there are a lot of things you can do one on one that are pretty wild and out there. When you start bringing third parties in the room, you upset the balance of what you already have. Sure, at first it's a helluva lotta fun, but it does change things, and not necessarily for the better.