I think this marvelous movie could hv been even more successful if they had answered some of the questions in the mysterious DC universe. The movie was an excellent dark thriller, but the reason for its extraordinary success ( as compared to other thriller movies ) was the well established and beloved character of joker... having fans almost equal to batman!!
This is why , we were expecting to see some connection between the earlier joker appearances: like his 'scars' , 'agent of chaos' or relationship with harley quinn...
It is really not pleasant , at least for me, to depict a completely new story in every new movie adaptation. Kindly start putting the pieces together. They should realize their main audience are the DC fans. This movie was not much related to that!
That being said , hats-off to pheonix to do justice to the character of joker , previously established by the legend Heath Ledger himself.... plot was nice , a dark feel was maintained throughout... nd I think they were successful in justifying the pains joker went through which led to his transformation
Conclusion : A Must Watch movie for the dark movie lovers... but dont expect it to be much related to the joker we know!