By far the greatest thing about Arkham City is the ability to glide freely around the city; coupled with a grapple boost move you get during the game, with minimum effort it is possible to stay in the air indefinitely. You just need to be careful not to get yourself in a bad situation. At first Arkham City seems pretty large, but that is deceptive as there is a large zone in the middle of the map that is cordoned off. Also, it doesn't quite feel Gotham enough for my taste. I suppose that's because it's not actually Gotham; it's a small area of Gotham that got sectioned off into a containment area for prisoners. I guess this fits more in line with what the game is about, but it would have been nice to be able to patrol Gotham proper. The only thing that bothered me about the flying was that they threw in some challenges to test your skills. They can be frustrating at times, and one of them in particular was a major bitch to get as you have to thread the needle. Advanced AR Training 1, kindly die in a fire.
I'm about halfway through the story and so far they've done an impressive job of including most of the major villains (and many lesser ones). I won't spoil the fun, but it really runs the gauntlet. I am a huge fan of the animated series, and this game like its predecessor has a very similar feel. I think my favorite thing so far has been the Riddler side missions. There are the usual hidden trophies and clues, but they've added a twist by having many of the trophies locked in different types of puzzles which require various gadgets or special moves to access. The only downside is that you won't be able to access many of these until you progress further into the game and obtain the requisite abilities. Still, they are fun. The best, though, are these side missions where you have to rescue hostages from Riddler rooms. It involves similar mechanisms as the trophies, but the puzzles are larger and more intricate.
Fighting mechanism is mostly the same, though there are even more moves available now (perhaps too many). They also introduced a few new types of enemies - so far I've encountered body armor, blades, and riot shields. Sadly they seem to have done away with the knives and electrified batons of the previous game; Shock and Awe was one of my favorite challenge maps from Arkham Asylum. I really like what they did with the riddle locations, though. Instead of finding a lame map, you interrogate certain prisoners for their locations. Basically you'll come across a group of prisoners every now and then where one of them will be indicated as the leader / informant / whatever. If you beat all the other guys up first then you'll be able to get the locations out of him. You have to do this a lot as there are 400 items spread across the city, but the challenges are varied enough that it never really gets old. You have the standard story missions and then there is a nice amount (and variety) of side missions. Honestly, I think they outdid themselves. I would have been satisfied if this game simply wasn't a letdown, but it's one of those rare gems where the sequel is actually better than the original. My only minor quibble so far would be that it seems all the enemies are tougher. It just takes more blows to bring down the average prisoner than it did in the previous game; that can kind fuck up your rhythm when you're dealing with a large group. Other than that, excellent.