Hi,
Apart from the obvious, being that there is a great gift in front of me.
There is also the fact that it gets me where I want to go, by ways of my sub/wife having the the her crotch rope sopping wet, the line of moisture running down her leg and the dampness on the top of her stockings, the odd drip on her toes or shoes should she be standing.
Or the massive wet patch shoud she be laying down.This more than anything shows that she too is where she wants to be. Showing me that I'm doing my part right.
The marks around her breasts after the rope is removed, and the colour coming back into them, or the slight marks around her mouth where the tape was removed.
The anticipation, of hoping that nobody notices the rope marks around her ankles, or the knees or her wrists. It's all a very mutual thing, these thing put me even more in love with her.
I also love the feeling of walking along the street knowing what she does, and that other women only "THINK" that have a good life.

I touched on this in another thread, where my wife/sub was listening to one of the girls at work rattle on about BDSM and having no idea there was a sub right there in front of her. She told me that this other girl not having a clue made her feel very NAUGHTY.
There is more, but this is a deep thread.