Patch 4.0.3a is here! Azeroth is changed forever! Or, will be, whenever it is the servers come back up.
This is likely the biggest patch in history. If you're looking for a detailed list of changes to the world, MMO-Champion's your best bet. Today, I'm going to talk in more general terms, and hopefully provide a few useful links for the more useful tips about the changes.
First of all, how have things changed for the various races? (Warning, some spoilers for the novel The Shattering.)
Tauren find themselves with a new, barely-tested leader. Baine Bloodhoof is young but very much his father's son, giving a promising new beginning. At the same time, they have found a new way of spirituality, worshipping the spirit of the sun and bringing in the ways of the Light. For their plotting to bring down Cairne and take over Thunder Bluff, the Grimtotem have been expelled from Thunder Bluff and all allied Tauren settlements. What will they get up to in their exile? I'm looking forward to finding out.
The Orcs also find themselves with a new leader, Garrosh Hellscream, who recently became the new Warchief of the Horde. He may be a warmonger, but he is what his people need. Ogrimmar was seriously damaged during the Shattering and the events leading up to it, requiring massive portions of the city to be rebuilt. However, Orc resources were already stretched way too thin before the earthquakes started, and now are on the verge of disaster. Garrosh has led Ogrimmar to rebuild with metal to replace the dwindling wood supplies, and gives his people hope by promising glory and honour. We'll just have to see if he can deliver, or if he's leading them into further destruction.
The Trolls have returned to their home islands and have reclaimed their honour as well as those they left behind, the new druids of the Darkspear tribe, even as Vol'Jin finds himself losing faith in the Horde under Hellscream's leadership. Can Garrosh and Vol'jin find their common purpose?
The Forsaken, up until now they've been focused almost entirely on defeating Arthas, Now that that is accomplished, they find themselves a new purpose in destroying the Alliance who despise them, and have found new allies as well in the Val'kyr, allowing them to replenish their numbers. But how will this change their relationship with the Horde, and can they deal with the Worgen on their borders?
The Humans have hit troubled times, having lost many to the war with the Lich King and with a King that is filled with hatred for Orcs and the Horde in general. Like Ogrimmar, Stormwind struggles with dwindling resources as they attempt to rebuild from Deathwing's attack, and King Varian puts more and more resources into the war effort. How will his people react, and will he change his ways?
The Dwarves, meanwhile, have their own problem. After King Magni Bronzebeard died in an attempt to communicate with spirits of the Earth, his daughter Moira returns and lays claim to the throne, bringing those Dark Iron she controls with her. After being talked down from trying to remove her from the throne by his son, King Varian orders the Dwarves to form a new council, the Council of Three Hammers, holding a representative of each of the three Dwarven Clans, (Muradin representing the Bronzebeard, Falstad representing the Wildhammer, and Moira representing the Dark Iron), and now we must wait to see if they can hold the peace or whether they are destined for civil war.
The Gnomes have taken back the surface levels of their home city of Gnomeregan. While the city proper is still contaminated and full of enemies, the Gnomes adapt and now live mostly on the surface outside of the city itself. Meanwhile, after discovering in Northrend that they share a very similar history to that of the Dwarves, some Gnomes have taken to following the Dwarven way and worshipping the Light.
The Night Elves have recently been gifted with the return of Malfurian Stormrage from fighting the Emerald Nightmare, only to have lost many to the Shattering and Deathwing. Meanwhile, the Shen'dralar have rejoined their Night Elf brethren, bringing magic back to a people who, on the whole, despise it.
As for the Draenei and the Blood Elves? Absolutely nothing's changed.
Now, onto gameplay itself. For the healers, here's some useful links to help adjust to the new changes.
Druids: http://www.restokin.com/2010/11/cataclysmic-resto-talents-changes-for-4-0-3a/ (Thanks to Tarinae!)