First off I loved the gameplay as Robin. That was extremely well done and in my opinion the best part of the dlc. I wish they could release an entire game around him. However, the rest of the game fell flat from there. It only took me around an hour and a half to complete and left me feeling cheated. There was a nice little insider on Harley's pregnancy, which is something that I regretted seeing. And another small Easter egg you can find if you kept talking to Gordon as Batman. However, they never follow up on either of these plot points or any sort of inside on why Batman is such a hard core dick, and agitated.
tldr: The lack of any depth ruined the possibility for new story/information about Harley, Batman, or the Joker. Making it a C- expansion at best, edging on a D if you wanted more quality story.
I will not buy them day 1 anyway.