Blizzard have added a lot of changes to the patch 2.3 notes.
There have been changes to all classes, as well as some Raids and Dungeons, including Karazhan:
Karazhan Chess Event: The Dust Covered Chest can now only be looted by players who are nearby when the event is completed successfully. In addition, the chest now contains 2 Badges of Justice for each player present.
Engineering changes:
The Crashin' Thrashin' Robot is now Bind on Use rather than Bind on Acquire so non-engineers can use them as well.
There are also several item changes:
Band of the Eternal Restorer: As this item now provides some bonus spell damage, spell damage effects can trigger it. In addition, healing over time effects can now trigger it when they could not before.
Eye of the Dead: As this item now provides some bonus spell damage, spell damage effects can now consume its charges.
Free Action Potion: The buff from this potion can no longer be dispelled or taken via Spellsteal.
Hallowed Wands: These items no longer work on Druids who are shapeshifted.
Hallowed Wands: These wands no longer function in the Old Hillsbrad Caverns of Time event.
Hallow?s End Pumpkin Treats: The larger and oranger buff no longer causes Battle Elixirs to be removed and can stack with them.
Lightning Capacitor: This item now has a 2.5 second cooldown on acquiring Electrical Charges.
Noggenfogger Elixir: Consuming this potion now has a shared 3 second cooldown with other types of non-combat potions.
Ogri?la Reputation Rewards: All epic and superior quality items are now disenchantable.
PvP Trinkets: Insignia of the Alliance, Insignia of the Horde, Medallion of the Alliance, and Medallion of the Horde now clear the debuff from Judgement of Justice.
For the full list of the changes, see here: http://www.worldofwarcraft.com/patchnotes/test-realm-patchnotes.html.