OK, if I was trying to sell this one it would be hard to pick anything specific and depends on personal likes and dislikes.
For me, I think that the humour is top notch, but I can see that would not be for everyone. I don't play these games to have a belly laugh, but this made me laugh out loud quite a few times. Second is the quality of the writing. I like a good story that I can get immersed in, and even the silliest plot can get you immersed when written well while a good plot does not save poor writing. Again a personal thing, but there is more eroticism within the eye of the mind than in the best of renders, and it is the writing that feeds and supports this. I never skip text and suffer through some poorly written scripts that really should be skipped, but well written dialogue really makes a game for me.
In short I would say that it does everything that matters pretty well: story, writing, character and plot development, renders and animations (if you don’t mind HS2).
I really was sad when I came to the end of the current content and can’t wait for the next instalment.