The ground takedowns were bugged and would frequently cause problems in combat freeflows, the lip synching was god awful, and there is a Riddler Trophy that you can only glitch your way to get it.Worst decision ever, because either way they would've needed to fix at least some of them to make sure that the DLC integrates properly.
I liked the Cold, Cold Heart DLC. Thought it was really good. Initiation was a chore though.