Single press and swipe right on the iPhone seems intuitive enough to me. The issue I have with the current shortcuts (using buttons) for photos in every phone I've tested is that the pressing of the button is 'stiff' enough it involves jerking the camera slightly, leading to blurrier photos than using the screen tap. Also, obviously, volume button (which tends to be the shortcut key...) is on the wrong side of the phone, generally.
Hopefully this special button is a lot less 'stiff' compared to the other buttons.
