PvP-wise, I'm just concerned, period. We already have problems with shields getting dispelled/spell-stolen as soon as they go up, our mana regen is, um, rather lackluster, and now it's also going to cost so much more to cast?
I seem to recall that there was a proposal for PW:S to apply a mana-increasing buff/debuff like Arcane Blast; wouldn't that be equally effective at discouraging shield-spamming while not punishing shields as much in normal situations?
I'm really happy that they're buffing Resto Shamans, though! Hopefully now the Resto Shamans I know can stop re-rolling Holy Pallies. :p