I’m not impressed. The initial disgust is more or less gone; this kind of change usually at first makes one think that the change was much for the worse and then quickly get used to the new design. But some objections remain. The rationale claims that they wanted something “free of excessive decoration and focused on your content” – the contrasting black left panel goes straight against this philosophy. And the font is much, much too big.
In combination with the claim that they are working on a responsive design for smartphones and tablets this makes me suspect that this is another step in the silly trend on pretending that smartphones can fully substitute laptops. No they can’t. Just as whatever you do, it will always be easier to carry a smartphone than a laptop with you, it will always be easier to read, write and edit on a laptop than on a smartphone.