We know that this is likely to be one of the most contentious and difficult changes in jQuery 3.0, so we wanted to put it out in this early release to see the effects.
The change? These methods would no longer do complicated checks to set/reset the display style on an element that had been altered via the show, hide or toggle methods.
They proposed a simpler model: show() would remove "display: none" from the inline style of the element, hide() would set it. That's it.