i too was skeptical using steemconnect but it is perfectly safe to use i know you give faith that steemit inc/ busy manage correctly but would be counter intuitive to mismanage as longterms gains far out weigh what having a weak safe guarding on keys
also giving your posting key only lets an application vote,comment,resteem for transfers can do manually and never give your master key and your perfectly safe from someone getting full control on your account and you can change at anytime