Also, I've been playtesting the Anti-paladin for two weeks now with two PCs. One is straight Anti-Paladin (level 3), the other is multiclassed Anti-Paladin 1/Fighter 2 (going to switch back to Anti-Paladin from level 4 on). The playtest shows them to be powerful, but not invincible by any means.
In my campaign, Anti-Paladins are an elite division of (evil) church soldiers created to serve as holy warriors, able to serve as inquisitors/spies (detection abilities) and loyal frontline warriors.
The class is a little overpowered, 'tis true, but is not (so far) outshining the standard classes.