I actually don't have too much of a problem with the spells themselves, just how people might optimize to really break them (I know, these are pre-broken). If you are playing a cleric and you want to swap out your armor feats, no problem. Good for you for knowing your spells, but ...
If you have a character jumping through multiple classes for the express purpose of getting armor feats to swap, IE throwing 1 level of fighter on your epic wizard at level 21, then I am annoyed.
What I like to see is:
1) Actually keeping some of the Abyssal feats
2) Taking feats of similar power, ie eschew materials, spell thematics, exotic weapon profiency, and stuff not generally used.
3) Forever lossing access to said armor feats or whatever, so if you swap it out you cannot regain it through another class.
4) No epic feats unless you convince me it falls into group 2 (maybe the DR bypass, or fast heal which is not all that by the time you qualify).
5) Only permament feats swapped and no multiclassing for feat swapping gains.
So overall you make a more interesting character and don't go with a power grab. I get the same feeling from fast spell progression PrC's. Neat classes, but I don't want to see more than one in a build that are both dual-progressed with yet a third PrC (I am looking at you too Master Spellthief Feat).