I certainly agree that, done correctly, RWD enhances usability on all platforms. But the cost of doing RWD "correctly" (device testing and experience optimisati

I certainly agree that, done correctly, RWD enhances usability on all platforms. But the cost of doing RWD "correctly" (device testing and experience optimisation across a wide range of devices) can be prohibitively expensive when developing anything more than a landing page. Any site that requires extensive user interaction (i.e. contains custom form controls, overlays etc.) requires that usage patterns be tailored to the context in which they appear. So at a minimum, you're going to want to change your interface based on whether the user is using a finger or a cursor. Screen size, browser capabilities etc. are all additional factors that a careful implementation needs to be aware of and adapt to.