Luckily I had Arkham City on Steam before they patched the crappy Games for Windows Live service out of it. When they did that they upgraded everyone to the GOTY edition. From what I remember, the Harley Quinn DLC was fun but I don't remember much detail about it.
I've always liked all the work the put into other characters for challenge maps. They include multiple skins for each of them and give them unique skills and weapons that make them feel different in combat. They do all that work and then restrict these characters to challenge maps. All I could think of when running Arkham City challenge maps as Nightwing is that it would be really cool to use him for missions that have an actual plot.
That was the main thing I remember from the Harley Quinn DLC. It was cool to play as Robin for actual missions instead of just challenge maps. The Catwoman missions were alright too but I'd like to see more of that kind of thing even if it's limited to DLC and not part of the main story. I realize that the story could get pretty convoluted if they let us play missions as Batman, Robin, Nightwing, Catwoman, Red Hood, Harley Quinn, etc...
That's why it's such a bummer that Arkham Knight made the Red Hood missions an exclusive pre-order bonus for Gamestop. I pre-ordered on PC and I get Harley Quinn playable in challenge maps but no Red Hood missions.
