I think this is an ugly, clumsy typeface, designed primarily for legibility in a particular small application (the watch). Now it's now rumored to be destined as the system font in 10.11.
Going from graceful, readable Lucida to ok-only-in-Retina-but-even-then-hard-to-read-and-overused Helvetica to this new San Francisco is just plain frustrating. Maybe readability trumps taste, but in that case, just go back to Lucida.