For me sex died when I began HRT, since my T levels plummeted below test limit of 1.5 nmol/l. Couldn't get erect, couldn't get sexually aroused. In contrast, before HRT I felt I had to masturbate once or twice a day to keep my cool. After - I felt no need at all.
There was one time during this period, first night in bed with my girlfriend that she massaged my breast for a long while and then eventually I felt a tingling that built up and up and up and felt explosive and was totally awesome and happened only in my breast area. But then I wasn't so shocked anymore from her being with me, so it didn't happen again.
Then after 9 months of HRT I switched from pills to gel, and my T levels went back to male levels within a month and I was able to have sex, and it was just like before, plus slight pain in the background during erections, possibly due to atrophy from lack of use. Now we raised the dosage, but it's too early to tell. I think I still have some of my sexuality but it is vastly weakened, but again... it's been only two weeks on the new dose so I don't really know. I'm definitely less horny now again, but now sure I am at rock bottom like before.
Never felt any new breast sensitivity except on that one "magical" night. But my relationship with my girlfriend is always magical as far as I'm concerned, whether we have sex or not.