I was really stunned by how good it was. I watched all of Batman: TAS first, and had seen some pretty amazing ****, but I just couldn't prepare myself for that ****. The looser content rules obviously did them all kinds of favors. And yeah, having Joker backstory and having it actually be good is both rare and cool.
I assume you're discounting Batman '89 since Burton like never read anything about Batman, if I remember correctly, haha. I did like the whole "I know you are but what am I" of the YOU MADE ME stuff though. Also despite the lack of reading/research Burton's Batman kind of reminded me of the original Bob Kane Batman, from what I know of him. Mostly like present-day Batman, but if he has a mind to or doing so would make things easier on himself, he'll totally kill a guy and not give a ****. That was interesting.
the important thing is that the joker is awesome and MOTP is awesome