I prefer it when there's a strong balance between seriousness and humor, like the DCAU and the Burton movies (and to a lesser extent Batman Begins, where it takes a long while for the humor to come in). I liked The Dark Knight, but I still felt it took itself waaaay too seriously (though there was some humor around the beginning, but disappeared by the time the plot got off the ground). Obviously no one's asking for it to be a straight comedy, but I'm sure most people going to see this wouldn't really want to see nothing but misery after misery with everyone either dead or broken by the end (which appears to be the case with many recent comic stories I've been hearing about, especially in the New 52).
At the moment I am too broke to see it in the cinema (not helped that the sole cinema in my current town requires you to buy tickets like a month in advance). So I might end up catching to spoilers through some wiki after probably a week or two like I've done before, though there's probably not much that hasn't already been spoiled by the trailers and other promos. One of the things that wasn't might be which Robin was the one that this Joker killed before the events of the movie. I want to believe it's Jason Todd, but I'm a bit worried the crew thought it would have been too obvious and instead went for Dick Grayson: part for unnecessary shock value, and part to pander to the Bat-fans who don't give a single fuck about Nightwing and would rather see "The" Robin burn in hell forever because of how he was presented in the 60s show and the Schumacher movies (even though Dick really needs an official live-action version that gets his character right). Then the "official" excuse would be just to show how vile this Joker can be in case people may have doubts over it before Suicide Squad comes out.
I want the next Batman movie to focus on the Bat-Family to some degree: Nightwing, Oracle, either Tim Drake or Damian Wayne as Robin, either Cassandra Cain or Stephanie Brown as Batgirl, etc. And preferably a villain that wasn't already in a previous movie. Maybe even do away with the whole "hero has superpowers and/or goes outside the law to catch criminals, therefore the world has to treat him as the real villain" thing. (Okay, that last one is more for the next hero to get a movie than anything else.)