There's always going to be "people"... you don't have to give credence to every opinion out there, and doesn't negate that fact that this movie is going to be a mess as far as I'm concerned. We can always be proved wrong, but chances are stacked against this movie being any good as currently presented.
And honestly, I don't recall the Heath Ledger opinions... this recent incantation of Batman was very protective of their casting choices, so even before I knew Heath was going to play the Joker, I was already showered with the multitude of viral content with awesome Joker visuals. Plus Batman Begins was a huge success, so I don't see the parallel you want to draw here with Ledger... or with Nicholson and Keaton for that matter, who were actual movie stars. It just doesn't equate.