I just came back from watching TDK again. The theater was packed again, this the second weekend of its release. I still thoroughly enjoyed the film and I find the Joker absolutely mesmerizing. As with many comic book films, the villains seem to be the more interesting characters in their extreme quirkiness and fiendishness. And, I can imagine that as an actor, the Joker really would be more fun to play than Batman.
This time I feel like I was noticing more mannerisms in the portrayal of the Joker that may have been (probably were) subtle homages to Jack Nicholson (not necessarily specifically to Nicholson's Joker, but to some of the qualities of Nicholson's voice and certain mannerisms). This, to me seems appropriate, given Nicholson's history with the Batman films and because, I feel like I've read somewhere, that Heath deeply admired Nicholson as an actor.
And, this time I was focused more on the fascinating dynamics between the Joker and Batman... Specifically the idea that the Joker had no intention of killing Batman. And that the wry statement of the Joker's to Batman - "you complete me" - is probably very true... that they each need a nemisis to have a purpose (or something like that). Or, that they represent an eternal struggle between good and evil. Furthermore, it seems like the Joker much prefers to toy with Batman and torment him.
This idea of an ongoing struggle between the Joker and Batman seems to be set up pretty clearly during the Joker's last scene while he's dangling off the side of the building. He says "I get the feeling you and I are destined to do this forever!" Which to me implies that the Joker could easily come back.
On another totally different note... This time, since I'd already seen the film once, I could spend more time focusing on backgrounds and details, etc. And, I noticed several very familiar buildings in Chicago! In at least two different prominent shots I saw a large office building that my Dad used to work in a long time ago when I was a little girl! And, right after leaving the theater I called my Dad to tell him about that, and he said that he actually saw some of the Batman filming sets and specifically lots of Gotham City police cars back when the film was shooting in Chicago. I hadn't known that until today! I'd never yet spoken to my Dad in depth about Batman until this afternoon.