I think I may have to start work on getting a couple of more achievements, most notably beating the game on NG+. Do any of the boss fights change, as in do the difficulty get harder too? I've heard something about using completely different tactics on Mr. Freeze on NG+ than on Normal difficulty.
On NG+, you have to use all nine takedown moves on Mr. Freeze. It makes it even more awesome.
Plus the fact that he disables detective vision. That was a tough fight.