Ok, Instant metamagic isnt too powerful after erratta, but if you use stacking metamagic then the "Improved Metamagic" ability is pretty gross (the same ability is an epic feat under the ELH), also it just gets a lot of other stuff that doesnt really apply to the class but serves to further buff it up (immunity to energy drain?).
Basically wizards give up very little to become incantrices, and even the feats they have to blow they get back in the form of bonus metamagic feats. Its win-win-win for wizards.
Technik