Reports did run that Nicholson warned Heath that the Joker was a dark place to go... These were later disproved as mere rumours when Nicholson countered by saying he'd never met the guy.

Besides, Heath's Joker is a lot darker and more psychpathic than Jack's protrayal.

I agree it's impossible to watch Ledger without a tinge of grief, sadness or perhaps loss, knowing we we do that this fine young actor is gone and this was his swansong. Well, actually his final performance will be in Gilliam's next movie, which hasn't come out yet, but this is the role that has the most porximity to his death.

It truly is a rivetting performance - probably (easily) the best villain since Hopkins in Silence of the Lambs. (Voldemort just doesn't do it for me...)

But honestly, I really didn't find Heath's Joker as menacing as I would have liked. He's too funny and quirky and interesting to really terrify me or get under my skin like, say Hannibal Lecter did.