The Limits of Man
It is surprising how the Joker manages to put Batman into a corner so many times throughout the entire film. For the most part, the Joker is just one man. And while he has robbed a bank at the start of the movie (outsmarting the bank, and also successfully eliminating all the other robbers as well), his resources are nowhere near as illustrious as that of Bruce Wayne (who is not only a billionaire, but also has people like Lucius Fox working with him). He does not even have the same physical fortitude or fighting prowess as Batman.
But despite this, in many parts of the film, the Joker manages to trap Batman in harsh conundrums and forcing the Dark Knight into choices that are morally unacceptable. While Batman is successful in foiling Joker's schemes, he never quite makes it through the film unharmed.
Without a doubt Heath Ledger's Joker is the stuff of legends. Despite being so different from the interpretations of the Joker in the comics, or in the popular animations of Bruce Timm, the TDK film version of Joker is one that is much loved by fans and film critics in general. He is both captivating and terrifying. His endless variations of his own origin (which is a major treat for fans of the comics), and his super violent approach to anything he does has turned Ledger's interpretation of the Joker as one that many fans love and appreciate. It also sets a high film standard that from the looks of it, Jared Leto will not be able to meet.
Batman and Choices
Despite the fact that it is often the Joker that puts Batman into the middle of disastrous choices for most of the film, it is clear that Bruce Wayne is also a broken man that lets himself open to a lot of potential harm. At first he banks on Harvey Dent to be the new man on the front line against crime -but despite Dent's strong passion for the law, Bruce should have known that Dent was also a viable target. Also, his refusal to accept Rachel Dawes' decision to be with Dent makes him seem a little too desperate.
The Champion in the Dark
The film depicts Batman's fighting style as one that fully utilizes the dark shadows all over Gotham. He is stealthy, fast, and efficient. And he does not hold back on using his various gadgets in order to gain the upper hand. This is most obvious especially during the earlier parts of the film when he breaks out the Batmobile's cycle.
Bringing in Harvey Dent and showing his transformation from the devoted attorney and into Two-Face is a sight to behold. We particularly like the way that even if it was The Joker who is responsible for Dent's disfigurement. The character and identity of Two Face remains intact (there's even a very understandable origin for the coin that he flips too).
A Legendary Performance from Ledger
Keith Ledger made a legendary performance of playing The Joker is the Dark Knight and it is was rather tragic that he died several months after filming the movie. It is ironic that arguably his best performance was his last before his tragic death. One of the scenes that has become infamous in the movie is the pencil trick comically reproduced on Youtube here - Dark Knight: Jokers Magic Trick.
The Hero This City Needs
Even if Batman has managed to bring down the Joker at the end of the movie, the damage has been done. Dent is no longer the heroic DA that he could have been, and Batman taken on the weight of Dent's crimes.
It can be said that this is Nolan's best Batman film. In terms of visuals and design, the movie shows a modern and updated Gotham but still retains much of the city's timelessness. This is even heightened by the fact that the third movie in the Trilogy, The Dark Knight Rises, is not very good at all and has lead to some rumours that the next movie will be a reboot which will follow the last video game Batman Arkham Knight.