Your spell power is now equal to 65% of your attack power, and you no longer benefit from other sources of spell power.
Your instant spells and totems cost 75% less mana and your shock spells cost 90% less mana.
Your melee attacks have a 40% chance to immediately restore 5% of your mana.
Mental Quickness is a passive specialization ability for EnhancementShamans that grants spell power equal to 65% of your attack power, but causes the shaman to no longer benefit from other sources of spell power. It also reduces the mana cost of all instant and totem spells by 75%, reduces mana cost of shocks by 90%, and grants your melee attacks a 40% chance to restore 5% of your mana.
Patch 6.0.2(2014-10-14): Removed. Enhancement shaman mana regeneration has been increased by 100% to compensate.
Patch 5.3.0(2013-05-21): Now converts 65% of the Shaman's attack power to spell power, up from 55%..
Patch 5.2.0(2013-03-05): Now lowers the cost of shocks by 90% (still lowers the cost of other "beneficial, instant, damaging and totem spells" by 75%).
Patch 4.3.0(2011-11-29): Redesigned. Instead of granting the shaman spell power, Mental Quickness now causes Enhancement shaman spells to behave as though the shaman has spell power equal to 55% of attack power. Enhancement shaman spells no longer benefit from spell power from other sources.
Patch 4.0.6(2011-02-08): No longer reduces mana cost of all instant-cast spells (notably, no longer affects Purge). Instead, it reduces the mana cost of instant beneficial and damaging spells, as well as totems.
Patch 4.0.1(2010-10-12): Changed from being a 3-point talent from being a passive signature talent/ability for Enhancement Shamans.