I will be looking forward to this. Though I hope they don't use Arkham as the game's map again. That would be stupidly redundant. I can understand maybe a very small portion of the game being in Arkham, but the rest of the game should explore Gotham or at least some other portion of Gotham.
I read some people weren't thrilled to see the Joker being fed an IV. But think about it. If the game is continuing from the first.. well.. The Joker got really f-ed up. He's not in good shape, and would be in need of recovery. The fact that he managed to escape again after all that happened in that game is plenty impressive enough.
I don't see him being a major baddy in the new game, but like always, a mastermind of chaos never-the-less. He could be a vital character in creating trouble for Batman (as he usually is anyway, which would create the story for the game), I just don't see him being a threat like he was in the first game.