The fact that the game is done (wow can't believe how fast they got it done, Valve could learn a few things from them lol) but are still taking a year to "polish" it.
Personally, I think this is pretty neat. On the one hand I can see how gamers will say: "but I want it now! It is done so release it!" But on the other, I can appreciate that a game dev is taking the time to polish it, which will hopefully mean less bugs and a very stable game plus who knows what graphics or physical improvements to the game in a years time, maybe they'll get some new fancy shader in there to wow us during this time, or maybe some new feature that will just really enhance the gameplay. Batman: Arkham Asylum was a very good game, the gameplay was great, the graphics were great and that game is still fun even today, if they spend this much time polishing Arkham City I see a very long lifetime for that game, but I do wonder if not having it out for an entire year will kill any buzz about it.