I can't speak for guys, but I know for me I'm nearly begging to cum everytime I get spanked. I love it. I can't really say why either, it hurts like hell.
I think because I know at the end of it, provided I was a good enough angel for him, I know the manner in which he rewards... and the whole time I'm getting spanked, I'm thinking to myself, mentally begging him to fuck me... and occasionally I do beg him. I think he likes it when I do that.
The most recent guy I've been with.. is really the epitome of vanilla. He isn't really dominating during sex. I have had to literally beg him to spank me... but not in the good way. Not like the man I spoke of previous, whom I begged for him to fuck me. (When I go close to an orgasm, he would begin spanking me during. I've never felt just a harder orgasm.. He said my muscles tightened up so much around his cock it was all he could do not to cum himself. ^_^ My Sir, as I called him, needed to spank a woman. He would become so turned on by the sight and sounds of a woman begging him to fuck her, or to spank harder so she could cum, that in time, it became what he needed as well.
Hope that helped you as little. Also, definitely talk with him before you get into the sexy mood. Set the guidelines beforehand, maybe over a drink, or something. Just to know where you both stand as far as what you're looking for in sex.