I think its a stupid feat. Our DM outfitted a Cleric BBEG with this feat (combined with quicken). He came walking in while we were fighting his Ogre bodyguards.
First he cast Blasphemy (his highest level spell), auto-dazing most of the party members, then he followed up with a Quickened Blade Barrier (his second highest level spell) across some of the PCs. Since the dazed PCs could not get out of the way of the barrier they had to suffer it for two rounds, killing one. Next round he cast Harm followed up by a Quickened Inflict Critical Wounds: another PC killed. He was only 13th lvl, we were 11th. But with him pumping out two of his most powerful spells a round, it was like we were fighting two 13th lvl Clerics, but with the additional disadvantage that you were unable to act between the opponent's actions. The DM then decided to let the Cleric 'flee' because he could see a TPK coming.
It was the second time we met the Cleric, and the first time we set him running quite easily. The DM changed his feats slightly (added Divine Metmagic) to make him more of a challenge, and now he was suddenly changed in a TPK waiting to happen. The DM agreed to put the regular metamagic level limit on Divine Metamagic from that point on.