Some of the specifics of the update:
New high-level armor sets: Blizzard has introduced entire new "rare" armor sets for all of the character classes. These armor classes are a combination of rare and epic-quality items, and are largely better than the "Dungeon Set 1" sets (i.e. Wildheart, Beaststalker, Shadowcraft, etc.) previously available.
The new sets are named Feralheart, Beastmaster, Sorcereris, Soulforge, Virtuous, Darkmantle, The Five Thunders, Deathmist, Heroism. They can be found in the five and ten man dungeon instances in the game. You can see both the Dungeon 1 and Dungeon 2 sets at a new Web page Blizzard has set up for the task.
Five and ten man instances: Blizzard is increasing the drop rates for some epic items (their example was Headmasteris Charge and the Runeblade of Baron Rivendare), and has increased the abilities of others found in these instances. The flip side is that the maximum number of people that can enter these dungeons has been decreased! Stratholme, Scholomance, and Blackrock Depths now allow a maximum of five players inside, and Blackrock Spire allows a maximum of ten.
Golden Experience: Level 60 characters donit earn experience for turning in a quest, but this patch introduces the ability to get gold instead of experience. Specifically, any quests done at maximum level will have their experience reward converted to a "healthy amount of gold."
Weather: Blizzard has finally added weather effects to at least some areas in Azeroth, including: Elwynn Forest, Tirisfal Glades, Dun Morogh, Darkshore, Alterac Mountains, Stranglethorn Vale, Feralas, UniGoro Crater, Tanaris, Winterspring, AhniQiraj.
More areas will get weather in future updates.
Mac-specific changes:
- Fixed a bug which could cause the sky to be improperly rendered when the UI overlay was shut off in full screen.
- Improved the Mac sound engine to handle "multiple simultaneous buff" events without excessive audible distortion, such as the Warchiefis Blessing in Orgrimmar.
- Fixed a bug which could cause doodads in the Dwarven District to be incorrectly fogged.
- Fixed a bug which could cause terrain to be improperly rendered if "Enable All Shader Effects" was on but "Terrain Highlights" was off.
- Fixed a bug which would sometimes cause a selection circle under a character to be drawn as a double image.
- Improved smoothness of mouse input for camera turns ("mouselook").
There are many, many, many more substantial changes in the update, including class-specific changes, item changes, new flight paths, changes to instances, interface changes, quest changes, profession changes, and more.
The update is downloaded through the WoW client, and weighs in at about 27MB. As of this writing, the realms are still down for the update, but are scheduled to come back up today.