1. Trust can only go so far. People who say the trust Nolan so much almost make think there's a religious cult going on. Nolan is a good director. "Insomnia", The Prestige", "BB" were all great, but that isn't going to make me just trust the guy to the point where he could or couldn't have a slip up here. After all, this is his first sequel. There only a few sequels that outlive and outdo their predecessors. Some are just carbon copies and others are just downright terrible.
2. He is reimagining a beloved iconic villain. And from fans his vision of the character is a polarizing and divisive one. Some love it, others don't, and some want some changes made. It's pretty much lukewarm. I'm not a fan of him not being perma-clowned, nor of his scarred face, but the costume and hair are perfect. And it seems Heath's got Joker's intensity and unpredictability downflat which is a good thing.
3. A thing that worries me besides the Batmen is Harvey Dent/Two-Face. I hope the movie doesn't just suddenly introduce him, give him a few scenes, then Harvey becomes Two-Face, and there's no dramatic growth and character development for him to go from good to bad. If it were to just continue off from movie 2 than it'd work, but introducing Two-Face early would be a bad move. I also would like to know if Harvey is cheating on Gilda, if Gilda is in it, or if he's just with Rachel. I also want to know if he's secretly got mob ties.
4. We don't hear much about Gamble, Maroni, or Bruce and Alfred alot.
Now with that being said...
I am looking forward to seeing Scarecrow again, the Tumbler and the Batpod (still a dumb name should just be The Bat Cycle), seeing Dawes, Loeb, and the mayor die, seeing the action-scenes, seeing Batman and Joker fight---that's what I'm pretty much stoked for. And I want to see Batman starting to rebuild the Batcave and relying on his detective and computer work.