During today's maintenance, there is a patch being applied to the live WoW realms. You can check out the 2.1.1 notes below; this is mostly a bugfix patch.
- World of Warcraft Client Patch 2.1.1
The latest patch notes can always be found at http://www.worldofwarcraft.com/patchnotes/
- Players will now be able to properly destroy the infernals in the quest,"The Fel and the Furious".
- Gladiator's Plate Legguards: Fixed a graphical display error.
- Fixed a bug that caused some systems to see terrain holes appear in the distance.
- Stackable items retrieved from mail will no longer automatically stack in your inventory. This has been disabled pending a future patch fix.
- Players will no longer see the flickering terrain issues that were introduced with 2.1.0 when the LOD system is enabled.