Apple's got a tradition of being very good at their human interfaces. There've been some notable exceptions (like the wheels on version 4.0 of the classic QuickTime player - which earned a spot in the Interface Hall of Shame). The basic problem there was a common one: they tried to make the app look and act like the physical object it was analogous to, despite the inappropriateness of the physical interface to the computer screen and mouse.
Lately though I've grown really tired of an interface widget that rampant in iOS and shows up in a few places in OS X too: the on/off "slider" switch (scare quotes intended). Here it is from the Time Machine System Preference pane:
Dumb and counter-intuitive. Sliding switches are OK in real life (though I like the old-school toggle switches myself and they more jump than slide), but with a mouse, they aren't nearly as easy to use as a button (which is probably why they act like buttons too). On iOS devices, where they do function like the real-world version, it's easier to simply tap them like buttons and avoid the possibility of missing the switch. (I'm not even sure that they did work like sliders in earlier versions of the iOS; I remember trying to slide them when I first got my iPhone and being unsuccessful. Maybe I was just missing the target.)
Variety is the spice of life and all that, but it shouldn't come at the expense of usability. So, Apple, when it works like a button, make it a button; when it doesn't work like a slider, don't make it look like one.