I was actually saddened when I saw people starting with their patches forcing Lucida back in OS X 10.10.

Helvetica was one of the things that made the iPhone so great.

Helvetica is neutral, timeless and easy to read. It's the perfect user interface font, especially the UI-optimized version OS X 10.10 is using.

As always, people just hate change.

That said, San Fransisco is a cool font, it just looks horrible as a computer font: too much space, and it's almost like all the characters look the same. But for a small device like a watch it's perfect.