Jakob Nielsen takes some time to analyze the overall benefit of responsive design. I don’t want to spoil the article contents for you but the overarching view is that he feels that ‘mobile’ and ‘desktop’ design issues extend far beyond layout.
I know we’re all head-over-heels for responsive design, but reading articles like this is good practice for our professionalism. You should check out his arguments and see what your personal stance on each ends up being. I think a lot comes down to the perception of the overall usability of the mobile Web. My personal opinion parallels with the feeling that a website can be equally useful in all of it’s full content glory regardless of the device you’re using. I can contrast that with the fact that I’m perfectly willing to read a 2,000+ word article on a screen smaller than four inches though. We’re not the majority.