I know that few will see it this way, but Medium is actually bucking the latest trends in developing for the web. While they followed one trend by developing a website which can be comfortably used on most screen sizes, they are also going against another trend: releasing apps which work on all platforms.
Medium released an iPhone app today, and not an HTML5 app (like the Kindle Cloud Reader) which could be used on other platforms. Given that Medium is arguably a trendsetter for web publishing and website design, that makes their move retro.
Don't get me wrong, I am not being critical of their efforts. I just thought that it was worth noting that they went for a single platform app rather than one which we could all use. Perhaps I am misreading the importance of HTML5 apps, or the value that brings, but I do wish Medium had broadened their focus.