Umm.
Well, I always hate it when pornstars aren't having a real orgasms and just kinda say "oh yeah" over and over again and scream in a really non-sensual tone. They probably can't orgasm for every dude, cause there are some fucked up looking dudes out there.
And all that masochistic stuff, is a big turn off, I'd rather not watch someone sound like they are getting killed when watching porn.