There's a lot of readers on Medium, Richard. There are a lot of very good writers on Medium, Danny. The 37signals (Basecamp) weblog is on Medium. Anil Dash of Typepad (and other fame) is there. James Altucher is on Medium but he also has his own WordPress site with the same content (for Matt Mullenweg fans, Altucher's latest podcast is with MM "Do you have your own internal code?").

There seem to be quite a few high profile defections as well. Jeff Goins most recent content is no longer on Medium (now on WordPress hiding dates and oh boy is the source code a mess and Disqus won't load) nor does Marc Andreessen seem to publish on Medium any longer.

It's a pity Medium is struggling so much with their business model. A really competitive platform would do WordPress a world of good.