First off let's keep this spoiler free.
I just wanted to let you all know Arkham City is an amazing game. I did not believe it could be better then the first game, but the main story played out really well. I was pleasantly surprised with everything they stuffed in there. After you complete the main story there are plenty of side stories to keep you going a bit longer. Everything you do in the game is worthwhile, riddles, challenges, etc all help out so you want to complete everything.