Haste is obviously the most valuable stat for an arcane spec mage (aside from spellpower). one of my guildmates is stacking his haste at the expense of other stats (crit and spell power). Currently he has 963 and says that he expects incredible results once he reaches 1000+. I always thought that the best dps resulted from favoring the most valuable stat but not stacking it to the point that it is detrimental to other stats i.e. having sp/crit/haste somewhat balanced (assuming hit capped). I'm not sure how to prove this