For me, Medium is perfect as it is. Having used the site to publish a few pieces myself, I’ve found the site easy to use, easy to invite others to help proof-read, and it’s also great to look at, with some nice image features and typography settings.
Luke Chesser, of Crew (formerly ooomf), has designed a new look Medium for fun, and something not to be taken seriously. Openly admitting that the design misses out 90% of the crucial features, Luke explains that the design is just a “bit of late-night typography practice.” Still, the design is a great one and captures the look and feel of what Medium is. It would be interesting to be able to upload images that helped dictate the look and feel of the piece, rather than just the header and a whole background image would help with that.