Devastatingly dark, it should be definitely more restricted than just a "PG." Thanks to creative co-authors, there is hardly any nudity, which makes the audience concentrate on a political/ethical issue of today - the rich gets richer.
It is in the increasingly dominating style of the present rulers that we find the city of Gotham in trouble. The villain's rhetoric against the rich reminds very much so of the Communist Revolution in the 1917. While the rhetoric is appealing and many people fall for it, it is also the tool of oppression. This whole ado serves as a warning to our modern population not to overreact in the current condition of deep recession that is not too far from the Great Depression of the 1930s.
You simply cannot undo the damage by adding more damage. That is something I learned form the movie. Batman, as a hero, brings back the balance by a self-sacrificial deed - carrying a nuclear bomb away on his plane. Following his action, Detective Blake, a soon-to-be Robin is emerged as another hero at the end of the movie. Now, that's the moment when the audience can ask a logical question - when will an alternative and, consequently, better version of "Batman Forever" emerge? With a powerful plot-writing and creative thrill of Nolans' superb visual effects, we MUST see their vision of the heroic union of the two - Batman and Robin.
Although a great movie finishing the trilogy, it has left me as a viewer with an unsatisfied thirst for more. Hence, the rating of 8.9 out of 10 for the sense of this incompleteness.