The first four levels are just not good enough to justify a 2 feat tax and four lost caster levels at that stage of the game. Coming at it from a spontaneous side, all Specialized casting does is compensate you for spells known you'd get from caster levels. Innate casting is ok, but on its own would probably not be worth a dip with a lost spellcasting level. Master of Metamagic and Limit Break are good, though Limit Break loses a lot because to really capitalize on it you need to spend yet another feat, Practiced Spellcaster. On the other hand the 20th level ability gets you enough that it alone would be worth a dip and two feats and the lost level all its own.

I think as it is, the PRC is just too backloaded. Here are my suggestions:

1) Have the +5 Perfection bonus to DCs at level 5 be changed into an ability you get at level 1 that gives +1 per class level. Think hard about adding in an ability that gives you +1 vs SR per level to compensate for lower CL with it (though see #2, in which case this is less necessary)

2) Give 2/5 spellcasting, with level boosts at 2 and 4. You may want to reshuffle the abilities so that the weaker ones (Innate Casting and debatably Spec Casting) are on the 2/4 levels.

3) Move the immunity to AMFs to Innate Spellcasting, since its the weakest ability currently and could use the buff

4) d6 HD and 3/4 BaB are unnecessary and unthematic, putting it back to d4 and 1/2 gives you some more moral authority to restore a couple of those caster levels

5) As it is Spec Casting is much, much better for a Prepared caster. The real slap in the face is that to choose it a spontaneous caster already needs to have 3 spells with the descriptor, so he ends up needing to have 10 total (and as a limited list caster picking 10 spells with one descriptor is pretty wasteful). If this class is just meant to be more of a Prepared thing that's ok I guess, but it really isn't nearly an equal feature right now, especially considering the power of a Prepared caster choosing [Creation] or something like that.