i have a feeling that, despite my better judgement now, i'll watch the movie, and while still lulled by the special effects, go and pick up the game. Sounds like it'll be an above average game, though better than most of the movie-to-game conversions we've seen before.
The "hacking" concept sounds like a debug mode. Essentially, there'd be different items like gravity, inertia, collision detection, etc. and you could change the values of them, likely at any point during the game. Since the Matrix is really just a detailed virtual world, it lends itself really well to this. If this is true, it could up the replay of the game a bit, at least for players willing to experiment.