Hey! Thanks for the kind words. Medium is a neat blogging platform with a focus on good quality content, although it is currently in its early stages and invite only.
The main concept in medium thats inspired me here, is their wysiwyg style editor (https://medium.com/about/df8eac9f4a5e) over markdown... although mine is a tad more minimal, I'd be lying if I didn't say they had a big influence on ZenPen.