The significant 2.4.0 patch for Diablo III is now live for PC, Playstation 4, and Xbox One in the Americas.  The patch features standard maintenance such as bug fixes, a revised buff bar, and item tweaks, but also adds a significant amount of new content to the game.  In particular, a lot of effort has gone into rounding out each individual character class with new abilities and further balance.

Perhaps the biggest new feature is the addition of the completely new Greyhollow Island area.  The island, once the center of an empire, is now a chaotic haunted ruin.  Greyhollow Island is a fully explorable new area which is available in Adventure Mode.  In addition to the new location, two previously existing zones have been updated to include new branch areas.  

diablo iii greyhollow island
Greyhollow Island

24 set dungeons have also been added, in contrast to the game’s randomly-generated dungeons.  These pre-generated, straightforward dungeons have been designed around specific class sets.  Master them to unlock exclusive cosmetic pieces for your character.  

Season Rebirth is another new feature which allows you to transform your experienced character into a level 1 Season hero, while maintaining your previously-logged hours.  PC users are also getting action combat, which was only available on consoles before.
A full list of patch notes are available at the official Diablo III site.