Light side and dark side - I usually prefer sex-positive stuff, especially where people choice's makes them end up in sexual situations, but there's a lot of fun to be had with playing up to the darker emotions tied up with sex - preconceptions of what's right and wrong, who you're supposed to be attracted to, fear of the consequences and the secret thrill at facing those consequences - all the little taboos that people set up for themselves. Breaking those taboos, especially if it's a gradual, well-built-up violation, has a lot of appeal to me...
...to a point. Straight rape or sexual slavery, especially if played realistically, is depressing and a bit of a boner killer. Same with a lot of the darker violence, drug use, and prostitution stuff. We all know people in real life suffer through that, and in the fantasy of erotica I tend to prefer people discovering themselves through sex, rather than moral degeneration into crack-addled whores, mindless bimbos, etc. Corruption and transformation should, to me, ideally leave the character as at least recognizable as their former selves, or else the point is simply degradation. Some people are into that, and it has its thrill, but it gets old. Some people never get tired of Wonder Woman getting tied up, raped, and impregnated, but at this point I'm more interested in Wonder Woman submitting gradually as a result of decisions she herself has made and rationalized in her own mind - to own becoming a slut, rather than to have it forced on her.
I also do like gender change, pregnancy, impregnation, and expansion - no surprise there for anybody that reads my stuff - although I try not to make it the sole and central premise. There's a lot of taboos and physical changes bound up in the whole idea of genderbending, impregnation, and pregnancy which I find fascinating - especially when developed over time, rather than some kind of instant belly inflation thing. I guess I'm just less interested in instant gratification than I used to be; I want to see people work through it.
