On Tuesday Blizzard rolled out the first major content patch for World of Warcraft since the launch of Wrath of the Lich King last November. The 3.1 patch includes the long-awaited dual-specialization feature, which allows players to quickly and easily switch from one set of talent choices to another. Action bars and glyph choices change as well. The patch also includes a new end-game raid dungeon, Ulduar, which expands upon the variable difficulty modes Blizzard has recently experimented with. The instance contains 14 bosses, 10 of which have an optional "hard mode" that players can attempt for better rewards. In addition, the patch contains a host of class balance changes, bug fixes, and UI improvements. You can see the full patch notes at Blizzard's website, and a brief trailer is also available.