When I'm playing with a delicious little subbie, my preference isn't to inflict physical pain, or to tie her up. I'm much more into the psychological aspects of dominance and submission.
The kinds of scenes I love often involve public play, prolonged arousal (on her part) and obedience/reward scenarios. Also sexualization of nonsexual acts; with enough training, it is amazing to discover the types of triggers that can cause a woman to orgasm... or delay an orgasm.
It's all about making her realize that her gratification depends on pleasing me, often in a manner that pushes her slightly out of her comfort zone... and her realizing that she's perfectly safe.
For me, this is what D/S is about. Anyone else?