Yeah, the "like me!" line is very important too. I love the fact that the Joker is trying to corrupt pretty much the only four incorrupt people left in the Gotham City. Batman, Rachel, Gordon and Dent. The Joker taunts Batman by comparing himself to him. Batman is the order and the Joker is the chaos. The Joker represents everything Batman is fighting against. And that's the Jokers way to send Batman over the edge. He's trying to convince Batman that they are two of a kind. Just two freaks. Two madmen fighting over the faith of the city.
BTW, I just watched the trailer for Batman Begins. Damn, such a sweet trailer! Bruce and Ducard fighting on ice, cop cars spinning in the air, Scarecrow gassing Rachel, the tumbler jumping from rooftop to rooftop, Batman kicking some ninja butt etc. Great stuff!