Well, I think that first kiss thing would be a great feature. It's adorable, and you're right about it being important. It's one of those significant enough firsts that people remember who they first kissed, myself included. In fact, a stolen first kiss can be extremely traumatizing. I should know, that's how mine went, and to this day I've maintained a dislike for kissing, as a result. That being said, I might not be a good example. I was five, it was a older neighbor kid (who coerced me into it), and it was a french kiss. Given the circumstance, it would be weird if that were a good experience. That being said, I think a pure enough PC would find a stolen first kiss major traumatizing, but a slut might only register that they lost another first.
Also~ did I beat you to it?