I don't know how I feel about the Joker being in the film. I mean, he's the iconic villain, and as such Batman will always have to live up to having to foil the Joker over and over. Which is why I was glad they didn't have Shredder for more than a meer mention in TMNT. The Shredder shouldn't hold up the franchise, same thing with Batman and the Joker.
As it stands he's been in 4 films.... Batman's 1966 film version of the series, Batman (1990) Batman the Animated movie Mask of the Phantasm (90's) and this upcoming one.
That's what I loved about Batman Begins. He fought obscure villains only Batfans would know, like Raj A Ghoul and Scarecrow. it was very exotic. But I'm sure they'll pull this one off with the same precision they did with BB.
I wonder if they'll ever make a movie about Killer Crock or The Mad Hatter.