I guess I knew this was coming. Still disappointed.
I can understand why some people are saying 'big deal'. The differences between sans-serif typefaces like Lucida Grande, Helvetica Neue and San Francisco can seem subtle when you're comparing individual letters. But even subtle variations become more noticeable when you see a larger block of text. A change to the default OS system font is a pretty big deal because it's so ubiquitous. It changes the reading experience, and the overall feel and character of the OS
in subtle ways yes, but on a grand scale.
When I started seeing the first screenshots of the Apple Watch, I thought the typography lacked elegance. It looked clunky to me. And it still does. It has replaced the round curves of Lucida Grande and Helvetica Neue with straighter, slightly more rigid letter forms:
That doesnt make it flow horizontally (the direction you read), so I disagree with the claim that its a marvel of readability. If anything, this kind of design makes the letters look more squashed together. What Apple has done, is compensate for this by increasing the default letter spacing. But overall it just looks inelegant and, I have to say, a little amateurish. (I appreciate that this is my subjective opinion.)
Apples decision to switch from Lucida Grande to Helvetica Neue in OS X was heavily criticised because Helvetica was never designed for reading on screen at small point sizes. In practice, I think it reads fine on todays high-resolution devices, although sure, there might have been better choices. I just dont think this new typeface is it.