So here's my male vision of it...
Not saying (or wanting to say) that sex is, everything in a relationship, I must say it is very important. As it is other affective manifestations or complicity in several other ways...

For me, sexual needs are very, very important. And it doesn't mean I would want to have sex with a girlfriend/wife regardless her will... I do not. I want her to want and I want my relationships to be complete in all ways including emotional and physical complicity and sexual expression...
As I write, I'm also thinking of Maslow's hierarchy of needs, represented as a pyramid with the more basic needs at the bottom... Sex is one of them... And it makes sense to me.
Having said that, i don't thing sex should occur in a meaningless way for one or both of the elements.. I don't think it should be used as a currency, although I try very hard to practice a continuous convergence of ideas and interests in my relationship...

Wish you all the best!