Both the launcher and log-in screen were updated to reflect Mists of Pandaria.[5]
New graphics options were added to boost visuals.[5]
Install size has been greatly reduced (under 19 GB).
File structure of install has been reformatted and access to cinematics/etc has been removed.
Game will now default to 64 bit client on x64 systems.
Abilities
Spells with long cooldowns (Guardian of Ancient Kings, Avenging Wrath) now reset after killing a boss.[5]
Mage portals and self-teleportation spells no longer require reagents.[5]
Pets can now be summoned and dissmissed while mounted.[5]
Mobs & NPCs
In Orgrimmar there are 2 new NPC goblins near the Engineering area.[5]
There is a level 91 elite puppy running around Stormwind Keep by the name of Crithto. That much isn't news, I guess; what is news is that he's now listed as a neutral non-combat pet, and will one-shot you if you accidentally hit him.[5]
Molten Core Corehounds were resized back to how they were in the past.[5]
Quests
If you go to turn in multiple quests to one NPC, it will automatically take you to the complete quest page for the second after completing the first.[5]
^Quintessence 2012-08-24. Patch 5.0.4 Reminders. Perks N Peeves. “Pet Battles. We'll have to wait until the MoP release date to access this new ability and minigame. The upside is that players do NOT have to upgrade to MoP to participate.”