It's possible there are still things to learn, but unlikely. If there were more people around poking at the code, we might have a better idea of whether or not everything had been found.
Really, what's more interesting to me is the question of how best to win IVAN (without cheating, of course). I guess I ought to give Al's guide a look and try some of it out sometime.
EDIT: granted, most interesting would be new versions of the game.
hint hint how's that coming along hint hint