It's well-made, and entirely captivating every time I sit down to watch it. But it's not without its flaws.
The Joker gets by as a character almost solely because of Heath Ledger's performance--he makes the character such a force of nature that you don't find yourself questioning the plausibility of any of his schemes until the film is over. Of course, once the film is over, I can't help but find myself thinking how he got all those explosives on the ferries without anyone noticing, among many other things.
Two-face doesn't really work. The justification for his coin-flipping philosophy from the comic book character never is explained very convincingly. You go with it because it's Two-Face, and the coin is to be expected. You also go with it because, despite everything pointing to the Joker being a dead man when he shows up in the nurse's outfit to confront Harvey Dent, you want Ledger to be on screen for as long as possible.
Still, it's very watchable, and the Blu-Ray looks terrific. And as far as comic book movies go (mainly, I mean to say superhero movies), most aren't going to be as good as (or better than) THE DARK KNIGHT.