I am glad you asked that question.
No i never have any manaissues, due to the massive +spelldmg increase from the specc.
My lifetaps raidbuffed give ma 2000+ mana, and with 1 point in mana feed you pet never runs out of mana either.
I even do fine witout a shadowpriest manawise, thou it is really nice for added petheal.
this is my specc:
Talent Calculator - World of Warcraft