Ah, looks like I'll be spending my Christmas with the Joker. Couldn't have asked for a better way to spend the day.
As for the extras on the dvd, I love the suggestions so far (commentary, viral campaign info, Joker/Batman relationship) and I'd also like to see a clip showing us a typical day of a TDK actor on set, from morning till the cameras stop rolling. This could include fun behind-the-scenes moments, little snippets of the actors and Nolan discussing the next scene, actors chatting and laughing on break, etc. Similar to "A day in the life of a Hobbit" that was on the LOTR: Fellowship of the Ring Extended Edition dvd.
Definitely another feature just for the script and its influences in comics and how the story came to be. This particular feature on the BB dvd was one of the most memorable to me. I could watch it over and over again.
I also wouldn't mind seeing Heath with his skateboard in the 'In Memoriam' feature (I'm sure there will be one). Hopefully someone took a picture of him, at least.