Jesus christ - this film, in IMAX, is an amazing fucking experience. Holy crap.
I don't understand quite how they decided which scenes would be regular size and IMAX, but however they did it, I applaud them. The high definition scenes were to die for, as was the whole movie. Definitely one of my favourites.
As for Heath Ledger's character, it was impeccably done, and worth the wait. He was such a nuanced character, that he even nailed the way such an insane person would sit down.
Also, the lines that referenced how as long as Batman would be there, the Joker would be there - they can't take those back now. Since we only saw Heath's face briefly, do you think they'll get another actor for the Joker with the makeup emulated? Or maybe greenscreen someone's face as they act and put Heath's appearance on it through the magic of computers? (A la Harvey Dent's later appearance? Well, half of it?)
Also, I know I'm a terrible person, but all throughout the movie I kept thinking that I should pick up The Animated Series on Amazon since they're all $17.99 PLUS promotion price. I ended up buying them all just now. It was like.. retrograde advertising. But honestly, it was my first introduction to Batman and my favourite, until this movie series.