Transcendent Spell is more than a bit useful with all the Free Metamagic tricks, such as DMM, Anima Mages, Ultimate Magi...
A Circle Magic Transcendent Greater Magic Weapon is a +10 Weapon, a Dragonskin is +20 AC, a simple Dispel Magic beats Greater Dispel Magic, Giant's Wrath is +40 to attack and damage... Yeah, I could use that feat better than Persistent Spell, by far, seeing as I can boost my CL to WAY, WAY, way, higher than what it should be, even without Circle Magic (we don't allow that...).