If you login right now you'll be able to download the whopping 1.3gb patch, thankfully if you've been running the background downloader the last few months you only should have to download a few hundred megabytes.

The most recent patch notes are located here.

Keep reading for a run down on what's to come in this patch...

New things:

• Barber Shops! You can find them located in Ironforge, Stormwind, Undercity, and Orgrimmar. More info on them can be found here.
• Achievements have been added! Have fun earning them and maybe some of them will give you cool mounts, tabards, pets and even titles!
• Stormwind now has a harbor! Enjoy taking a leisurely boat ride from Auberdine to Stormwind! And in the future to Borean Tundra!
• Vanity pets and mounts have been moved out of your bags and have entered the all new pet interface on your character screen. This frees up mucho bag space!
• A new in-game calendar has been added, you can use this to track holidays and raids or whatever you want!
• The amount of experience between 60 and 70 has been adjusted, enjoy faster leveling!
• Badges and pvp tokens have moved to the new token interface in the character window, even more bag space is freed up!
• The Caverns of Time has opened up a new portal, but you won't be able to enter it until you reach a higher level. Here you will go back in time and help Arthas in the Culling of Stratholme.
• Spell damage and healing have been merged into one stat called spell power, all healing gear has been lowered but now gives equal spell damage and the coefficients on heals have been raised to allow the same amount of healing.
• All items that gave one school of spell damage have been converted to normal spell power, such sets as Frozen Shadow Weave and Spellfire.
• All TBC raid mobs have had their health reduced approximately 30%.
• Illidan no longer shears!
• Tons of class changes and new talents! We get a free respec!
• Two new arenas have been added and we can play in! Queue up today to visit Dalaran Sewers and the Orgrimmar Arena!
• New honor rewards have been added at level 70!
• Macros and keybindings are now stored server side! We can now switch computers without rewriting every single macro in existance!

That's about everything new, more will be added as it is discovered but this should be about everything new!