Story time, Spoilers Time:
With the game now complete it's time to talk about the overall opinions of the game, and that is difficult to do without some spoilers. While I'll avoid 'major' spoilers I will be discussing some of the characters the make an appearance in the game and the flow of the story.
The story ties in well with Arkham Asylum, and the story focuses Joker's deteriorating health from his use of the TITAN serum. Batman is coerced into tracking down a cure, and through that quest for the cure he is exposed to the various warring factions in Arkham City, all while Protocol 10 is ominously counting down.
I'm not going to spoil the ending, but it was absolutely fantastic, and easily puts the game among my favorites.
The Supporting Cast:
While the main story showcases an impressive catalog of Batman's enemies and associates, the side missions do an excellent job giving other characters appearances in the game. Bane is around to address a TITAN problem, Riddler makes a return with his trophies and challenges with a much greater amount of face time, Zsasz returns with a game of phonetag, and Deadshot makes an appearance as an assassin eliminating key witnesses around the city. Several other characters are also around, and the face time for Batman's enemies seems to be greatly increased. While in the previous game the villains seemed to show up to present periodic boss-fights, the build up and payoff seems far better in Arkham City. There is a glorious segment where the Mad Hatter makes an appearance, and even with his being one of the shortest side missions, he establishes his menace quite soundly.
So Many Toys:
By the end of the game Batman's impressive arsenal of gear grows quite large, and there is even a slight quip from Alfred about why he didn't take everything with him in the first place. The game seems to make an effort to emphasize multiple uses for his tools, to give everything both a utility and combat use. It can sometimes feel a bit clumsy with so many options, but at the same time the options give the game a strange sense of depth that makes both exploration and combat interesting.
The plot of the game was fantastic, with several extremely dramatic moments and epic reveals. The boss fights were varied, and didn't overstay their welcome. (I'm looking at you Killer Croc segment in Arkham Asylum.) The side missions added a wonderful distraction from the main plot, and made the City come to life as things happened all over the City as the various villains went about their plots. Overall there were very few criticisms I can level against the game, other than the brevity of the tutorial. I'd strongly advise this game to anyone that enjoys the Batman franchise or enjoys other adventure/action games.