Finished it just there this morning. I'm not really sure about it yet. On one hand I enjoyed myself, but on the other, I can't shake the feeling that I preferred the first one over this new installment.
The combat is definitly improved, it's much funner now and a lot more satisfing to beat some skulls with your brain bashing bat fists. The bosses are better too, actaully being unique now rather than exactly the same thing over and over again like in the last game. The fight with Mr. Freeze is probably one of my favourite parts of the game. The bosses were probably the greatest problem of the first game, and I'm glad they improved that aspect in this game. I also like the improved riddler challanges, they made it more of an actually challange rather than to just crawl about and pick up trophies.
As for the story... Well, it was interesting. I just wish it didn't have to focused on the Joker so much. It kind of deals with Hugo Strange, but I think they gave Joker gets too much attention. Give someone else a go, man! I was getting excited about fighting two-face, but after a limp five-minute mission you never see him again. Noooooo! Well, you do deal with him more in the Catwoman stages, but come on, he's a big villan the series! He's tossed aside to be used as a marketing ploy, he deserves better than that.
Anyway, I like the setting, but it spread itself a bit too thin, and opened itself up too large in the beginning. Those used to the small courtyards and cramped corridors of AA will probably get freaked out by how open the map is from the get-go. There's so much to do that you don't know where to start, and that's more negative than you might think. And that's the thing I think; it throws so much in your face that you don't know what you're doing.
Nevertheless, I did enjoy it, and I think I need some more time to let it settle in my brain.