Mark Gurman reports that iOS 9 and OS X 10.11 might very well get the San Francisco Font, currently used on the Apple Watch. If true Helvetica Neue will go down in history as the George Lazenby of Mac fonts. Given that Apple designed the San Francisco font, I would not be least bit surprised if they brought it to all of their platforms. (John Gruber points out that San Francisco is now the font used on the new MacBook keyboard.)
I like San Francisco on the watch. It is clean and clearly designed to be on a screen and not piece of paper. I have no idea how San Francisco will look on the phone and Mac, but I'm curious. I'm probably not the person to make such decisions though since I was a fan of, and actually turned in a college paper using the original Mac San Francisco font. Yes. This one.