I've done it several times. But I've discovered I like it most when it is done in a dominating way. In other words, the girl might say I will let you cum, but only if you worship my ass first. However, the best was in a mild D/s session, when she said I better not have to tell you what to do. And she crawled on the bed, ass in the air. Yes, I knew I was supposed to dine. I'm not too ashamed to say that I came while worshipping there.
Had the exact same experience with a GS. Was told only way I could cum was if I obeyed. Told me to get in the tub and play with myself. When aroused, called her into the bathroom. She unleashed all over me--face, chest, cock. I was done within seconds.
I always like it best when it is HER idea and it is a surprise. Following scripts just don't work for me.