Hot. Very similar to my first actual experience. My conservative (to the point of being a prude, except when she was aroused) wife urged me to stop at a nightclub on our way home from dinner one night. As we were about to get out of the car, she took my hand and put it up under her dress to reveal that she had no panties on (and was dripping wet). I wanted to race home, but she insisted on going in.
One of the men she danced with starting moving his hands around on her hips and ass, discovering that she wasn't wearing panties, and the flirting and provocations escalated from there. The three of us ended up back at his nearby hotel room where I watched, my heart pounding through my chest as she undressed, lay on the bed and spread her legs, holding her pussy open for him to penetrate.
He was super cool in how he handled it. He paused just before entering, turned to me and said, "I'm going to fuck your wife now." Then he held himself in a position so I could see him enter and come out of her all wet a few times before he continued to fuck her for his and her own pleasure. Super hot.