I think this depends on what you mean by graphic. If you are mentioning the primary body parts and the general movements, in order to say more than "they had sex" or fade to black, more people may appreciate the writing. For a mainstream audience, I think there is a limit. Describing detailed regions within the body parts, fluids, sounds (verbal and otherwise), motions, technique, may be too much for some. I am not talking about taboo acts, just highly detailed descriptions. A play-by-play interaction between a fingertip, another body part, a conversation of the ilk "do you like that?" may be an abrupt change for some people.
I think you need to set the tone early in your book. Not by being salacious, but by not sugar-coating anything else that would be considered controversial.
In short, I dunno. Post a sample in the NC-17 section and we can tell you more.