A significant difference, though, is that while the early versions of San Francisco’s opening quotes were slanted down and to the right (like Verdana’s), the final versions are slanted down and to the left, just like its closing quotes. The only difference now between San Francisco’s opening and closing quotation marks is the tapering. The ticks of the opening quotes are fatter on the bottom, while the closing ticks are fatter on the top. You can see that — maybe — in the iOS 9 keyboard.
I have very few quibbles with San Francisco, but the shape of its quotation marks remains on the list. I don’t think they’ve ever been especially nice. Curly quotes are wrong for the rest of the letterforms; the Verdana-style ones that are in the released version are more apt, but still not very nice (and, as Drang points out, confusing).
Update: The good doctor has written more; specifically, as it turns out, about the poor automation of smart quotes in most software.