Catacombs does polish DAoC up a lot, the new classes unbalance things a bit too much sadly and put it back to being as unbalanced as the old savage days (Warlock DoT can kill anyone with upto 1800hps from 2500+ range away if they don't manage to get heals, also as well as their chambers they can do 5 uninterruptable casts meaning they can easily solo about 3/4 people at once. Hopefully Mythic will sort it out soon though, but then BDs, never got sorted out so perhaps not

The models are mostly pretty crappy, I and most people I know have turned them off but those are the only bad points really - the new classes imbalances and the crappy new models.
All in all it's pretty good other than that though, tbh other than the new classes you wont notice any difference if you RvR, it's purely a levelling expansion just with a few nice new +stat cap items. In the grand scheme of things the new classes have gone a long way to balancing populations - everyone wants a bainshee/warlock/vampiir whilst no one wants a heretic so that's pretty good for the game in general as it means Mythic can now start working on overall realm balance without having to worry about the population effect on that. Oh and Darkspire is damn good fun to do once in a while, it's a pretty fun challenge for a decent full group.