The majority of today's changes streamline interface elements, such as the character, spellbook, and guild management screens. Also, hoping to adjust how players choose and play their roles in-game, 4.0.1 has shed some of the bloat that has built up over the previous expansions. Rarely-used spells have been removed, talent trees have be redesigned and shortened, and the glyph system has been refined.
Several new features have been launched as well: "reforging," which allows players to alter the stats of their gear and replace less desirable bonuses with others that better suit their spec or play style, and a new water rendering system, which adds a nice cosmetic improvement to one of the game's most outdated-looking elements. A list of all changes made in the patch can be found here.