Turn off audio coming from mystery tabs
Forget searching for whatever tab a miserable ad is auto playing from, because the new Safari features the option to mute a single tab (or all of them) by clicking the volume icon inside the browser's URL window.
See less of the wheel-of-death thanks to performance enhancements
Thanks to some big behind-the-scenes improvements, you should also notice much speedier load times for things like launching and switching apps, opening PDFs, and accessing email. Though should you end up with that troublemaking spinning rainbow, you'll at least be looking at a visually improved version, since they updated the look of that, too.