LokiDR said:
Persistant is like permancy without exp. costs that can be used by clerics and druids. Since when are meta-magiced spells supposed to be better than the higher level spells the coexsist with? I would certainly say that is the case for persistant shield, divine power, and improved invis.
Actually, metamagiced spells have always been "supposed to be better" than most spells of the level they end up. That's why meta-magic feats exist (and cost a feat that could have been spent on spell focus or spell penetration). An Empowered fireball ought to be better than cone of cold at level 9 or 10. It costs a feat to cast Empowered Fireball. It doesn't to cast Cone of Cold. (Note that there are disadvantages associated with the empowered fireball--save DCs and Minor Globes of Invulnerability but it does approx. 5d6 more damage). An Empowered Bull's strength is supposed to be as good or better than Improved Invisibility or Divine Might. In the same way, a heightened disintegrate ought to compete with Finger of Death and a Persistant Shield is supposed to be a reasonable alternative to Wall of Force.
If there is an objection to Persistent Spell, it shouldn't be on the basis that it makes better spells than other spells of level X+4 (Note that the erratta rules out Persistent Improved Invisibility since that spell is Touch), Extend Spell and especially Persistent Spell have other effects that differentiate them from Still, Silent, Enlarge, Heighten, Sculpt, Empower, Maximize Spell etc. They generally are used with buff spells to enable parties to always be prepared. Thus Extend Spell enables a mid level sorceror to constantly have Endure elements running and a high level sorceror to constantly Energy Buffer active at negligable cost in spell slots. Similarly, it enables a mid-level wizard who knows about a battle in advance to cast his buffs one or even two days before the battle actually occurs. Since that is something that higher level spells generally can't do, there's no direct comparison like there is with Empower Spell. Extend Spell, however, is primarily useful for spells that are long duration anyway. It may reduce the opportunity cost of buffing and enable more buffs to be cast but it doesn't make short term buffs into long term buffs. Persistent Spell, OTOH, takes effects that were supposed to be extremely short term (Divine Favor, Divine Power, Righteous Might) buffs and turns them into all day buffs (I'm personally not sure that this is unbalanced in any case except Divine Favor and possibly Divine Power; If a 17th level cleric wants to be large all day, I think that's easier for a DM to deal with than Gate, Miracle, or the other things he could be doing with those 9th level slots--heck, he could use miracle for Tenser's Transformation (on top of Divine Power)).
However, the one use of Persistent Spell that strikes me as the "Most Likely to Wreck a Campaign" is the one nobody's mentioned: Persistent Detect Thoughts. Granted, it wouldn't have much effect in a purely hack and slash campaign but in any kind of a social campaign, it would probably have a more dramatic effect than any other PC capability.