I have, maybe 3 or 4 times, but then I have a fertile imagination.
Trying to get into the mindset is difficult but once there it was very hot though perhaps for its novelty, I don't know. I do recall a feeling of vulnerability, a sense of needing to feel trusting, but also of wanting to feel something in the male partner beyond his physicality. As I was imagining myself not having a penis I felt that I had to be passive and that was a little scary because I didn't imagine there was as much I could do physically. Yet I also noticed that men felt so very different. The harness of the muscles, the contrast of the delicate and soft skin of the penis contrasting with the rough and hairy skin of his body and face. I sensed an innate strength that I fairly worshiped. Too there was a desire to sense what he was feeling, as if I was trying to tune-in to what he was thinking, desiring to know what he really wanted. I have to say I was fascinated with his cock. Seeing it grow and become hard, and feeling him penetrate me just took my breath away. I understand now how amazing the cock must be to women. It's a great thing!
When he came it was just a rush. Feeling him pump his sperm into me, seeing and hearing, smelling, and touching him just at his most vulnerable moment was intoxicating; as if I was seeing deeply into a part of masculinity that was ordinarily hidden yet fascinating to me. It felt very feminine to know that his semen was in my womb and I would be feeling his semen inside me, dripping out, spreading throughout my uterus and vagina, as if I was fulfilling part of my womanhood. It was quite sexy and made me feel euphoric.
Despite all that, I have never had a desire to be a woman. I intensely love being male though I imagine I'd try being a woman for 3 weeks just to see what it's like if I had the opportunity.