It's pretty much an episode that pays tribute to Dick Sprang, Bill Finger, Batman (66), and Frank Miller.
IMO it's a helluva a tribute to those four. In the commentary track for the episode, Bruce Timm talks about how he recieved numerous phone calls from Frank Miller - who talked about how he loved the episode and he recieved a personal letter from Dick Sprang, who thanked him. Less than a year later, Dick Sprang sadly passed away at the age of 85.
Oh and they also take a stab @ Joel Schumacher during the episode so it gets even more of a from me.