IMC we use something very similar to the UA variant, with four "Paladin" subclasses: the Guardian (LG), Crusader (CG), Blackguard (LE), and Shadow Knight (CE). Anything saying "Paladin" refers to all four subclasses.
The differences:
1> The "Smite" and "Detect" abilites are switched to the Law/Chaos axis. We really hated how Detect Evil became carte blanche to attack things.
2> All of the disease immunity/removal abilities are removed.
3> When he first gains spellcasting ability, each Paladin selects one domain of his patron deity. He can now swap any spell for the domain spell of that level, in a manner similar to how Clerics swap.
4> The mounts were completely reworked to be more useful at high level. I posted it on these boards way back three years ago
here, but we've updated it a little since then. For one thing, we now have half the abilities come at even levels and the other half come at odd levels, so you always get something at each level.
5> "Avenger" weapons come in all four varieties (Holy, Unholy, Chaotic, Axiomatic); each Paladin subclass qualifies for two based on its alignments.
6> "Fallen" Paladins can switch to one of the other three subclasses if their alignments shift far enough, using Atonement to gain the analogues of the abilities they lost.
Other than that, most of our changes were similar to those in the UA versions, so when those variants were put in the SRD we changed parts of ours to match.
